Once-Daily Valacyclovir to Reduce the Risk of Transmission of Genital Herpes
http://www.100md.com
《新英格兰医药杂志》
ABSTRACT
Background Nucleoside analogues against herpes simplex virus (HSV) have been shown to suppress shedding of HSV type 2 (HSV-2) on genital mucosal surfaces and may prevent sexual transmission of HSV.
Methods We followed 1484 immunocompetent, heterosexual, monogamous couples: one with clinically symptomatic genital HSV-2 and one susceptible to HSV-2. The partners with HSV-2 infection were randomly assigned to receive either 500 mg of valacyclovir once daily or placebo for eight months. The susceptible partner was evaluated monthly for clinical signs and symptoms of genital herpes. Source partners were followed for recurrences of genital herpes; 89 were enrolled in a substudy of HSV-2 mucosal shedding. Both partners were counseled on safer sex and were offered condoms at each visit. The predefined primary end point was the reduction in transmission of symptomatic genital herpes.
Results Clinically symptomatic HSV-2 infection developed in 4 of 743 susceptible partners who were given valacyclovir, as compared with 16 of 741 who were given placebo (hazard ratio, 0.25; 95 percent confidence interval, 0.08 to 0.75; P=0.008). Overall, acquisition of HSV-2 was observed in 14 of the susceptible partners who received valacyclovir (1.9 percent), as compared with 27 (3.6 percent) who received placebo (hazard ratio, 0.52; 95 percent confidence interval, 0.27 to 0.99; P=0.04). HSV DNA was detected in samples of genital secretions on 2.9 percent of the days among the HSV-2¨Cinfected (source) partners who received valacyclovir, as compared with 10.8 percent of the days among those who received placebo (P<0.001). The mean rates of recurrence were 0.11 per month and 0.40 per month, respectively (P<0.001).
Conclusions Once-daily suppressive therapy with valacyclovir significantly reduces the risk of transmission of genital herpes among heterosexual, HSV-2¨Cdiscordant couples.
Herpes simplex virus type 2 (HSV-2) causes a chronic genital viral infection characterized by high rates of clinical and subclinical reactivation in the genital mucosa and the attendant risk of sexual transmission.1,2,3,4 Both symptomatic and asymptomatic reactivations of HSV infection have been shown to result in sexual transmission.5,6,7,8 Population-based studies in the United States indicate that 22 percent of adults have antibodies to HSV-2 and that an estimated 1.6 million new cases of HSV-2 infection are acquired yearly.9,10 HSV-2 has become the most frequent cause of genital ulcer disease in all regions of the world.11,12,13,14
Transmission of genital herpes to others is the chief concern in persons with known genital herpes.15,16,17 Although antiviral agents have been shown for nearly two decades to reduce the frequency of clinical reactivation of genital herpes,18,19 only more recently has it been shown that daily antiviral therapy also reduces the frequency and amount of HSV that is shed subclinically on genital mucosal surfaces, the principal source of transmitted infections.20,21,22 This reduction in subclinical shedding provided the rationale for our randomized, placebo-controlled trial, which was designed to determine whether once-daily valacyclovir could reduce the risk of sexual transmission of genital herpes.
Methods
Study Population
We enrolled heterosexual couples who were serologically discordant for HSV-2 infection from 96 study sites. The inclusion criteria for the HSV-2¨Cseropositive source partner were an age of 18 years or older, presence of recurrent genital herpes with fewer than 10 episodes per year, and nonuse of any daily antiviral therapy. The inclusion criteria for the susceptible partner were an age of 18 years or older and HSV-2 seronegativity on Western blot analysis. The relationship between the source partner and the susceptible partner was required to be monogamous. Both partners were required to be immunocompetent and in good health and the couple to be using effective contraception.
Study Design
The partners signed separate informed-consent forms that had been approved by local institutional review boards. The partners were seen together at the screening visit, separately at randomization, and at monthly intervals during the eight-month study period. The HSV-2¨Cseropositive partners were randomly assigned, in a 1:1 ratio, to 500 mg of valacyclovir once daily or to matching placebo.23 At each visit, safer sex practices, including the use of condoms during sexual intercourse, were discussed with each partner, and standardized counseling was provided when signs and symptoms of genital herpes were recognized.24 Condoms were provided free of charge to all participants in the trial throughout the study period. For the source partner, adverse experiences and recurrences of genital herpes were recorded on diary cards and reviewed at each clinic visit. The source partners were asked to come to the clinic during recurrences for which episodic therapy with valacyclovir (500 mg twice a day) for five days was offered.25 After the five-day course of valacyclovir had been completed, the source partner resumed taking the randomly assigned medication.
Source partners at four centers were invited to participate in a substudy to define the frequency of reactivation of HSV-2 infection in the genital region. Participants in this substudy were instructed on how to swab the genital secretions every day for two months. Women swabbed the cervicovaginal, vulvar, and perianal regions, and men swabbed the penile skin and perianal area.4,20,21,22,26 The participants placed the swabs in polymerase-chain-reaction (PCR) buffer and delivered them to the clinic at the next scheduled visit.
During monthly visits by the susceptible partner, serum samples were collected for HSV analysis, and diaries were reviewed for notes concerning sexual activity, condom use, and symptoms suggestive of incident genital herpes during the preceding month.5 The susceptible partners were instructed to visit the clinic if they observed symptoms or lesions compatible with genital herpes. Separate swabs of genital secretions were obtained for HSV culture and HSV DNA detection by PCR and were shipped to the central laboratory at the University of Washington.27,28 If new genital herpes was clinically diagnosed, patients were offered treatment with a licensed dose of valacyclovir.29
Study End Points
Acquisition of HSV-2 infection was defined as the isolation of HSV-2 in culture, the detection of HSV-2 DNA, or HSV-2 seroconversion in the susceptible partner during the course of the trial.2,5,8,15,16 Clinically symptomatic genital herpes was defined according to the presence of clinical signs and symptoms and was confirmed by isolation of HSV-2 in culture, detection of HSV-2 DNA by PCR, or HSV-2 seroconversion. An end-points committee, whose members were blinded to the treatment assignment, reviewed all cases of genital herpes clinically diagnosed during the study. This committee also reviewed all cases in which the susceptible partner had an abnormal genital symptom or sign during the study, as well as all cases of genital herpes confirmed by laboratory analysis.
Laboratory Analyses
All serum was sent to the central laboratory. Serum samples obtained at the time of screening, at the time of randomization, and at one month and eight months were run in parallel on Western blots. Seroconversion was defined according to previously published criteria ¡ª namely, the development of one to four new bands, including bands corresponding to HSV-2 glycoprotein G type 2 (gG2) or to HSV type 1 (HSV-1) glycoproteins, such as glycoprotein G type 1 (gG1).5,8,15 Cultures and PCR analyses for HSV were performed as previously described.4,26,27,28 All isolates from susceptible partners who acquired HSV-2 were tested for their susceptibility to acyclovir by the plaque-reduction assay.30
Statistical Analysis
The predefined primary end point was a laboratory-confirmed, clinically symptomatic first episode of genital HSV-2 infection in the susceptible partner. Secondary end points included the time to overall HSV-2 acquisition (i.e., the occurrence of the primary end point, HSV-2 seroconversion in the susceptible partner, or both) and the time to a first recurrence of genital HSV-2 in the source partner. A 3 percent rate of clinically symptomatic genital herpes (annualized rate, 5 percent) was assumed for placebo.15 Because this study was designed to detect a 75 percent difference between valacyclovir and placebo in the rates of clinically symptomatic disease, we estimated that 28 confirmed cases of genital HSV-2 infection were required for 90 percent power with a two-tailed test of proportions at the 5 percent significance level.31 It was estimated that random assignment of 750 couples to each treatment group would achieve these assumptions. Randomization was performed at a central site in blocks of 10 to ensure balance between the groups. Randomization was stratified according to the sex and HSV-1 status of the susceptible partners.
The two study groups were compared with respect to the primary end point with use of the stratified version of Fisher's exact test.32 Analyses included data from all the subjects who had been randomly assigned to a study group and who took at least one dose of medication. No interim analyses were planned or conducted. The study groups were compared with respect to time-to-event end points with use of the log-rank test, with stratification according to the susceptible partner's sex and HSV-1 status on screening. Hazard ratios were calculated by means of the Cox proportional-hazards model, with covariates defined according to stratum and treatment. Data for subjects who did not reach an end point were censored as event-free periods ending on the last day that the absence of the end point was confirmed. Interaction tests were used to determine whether there was evidence of a differential effect of valacyclovir treatment across subgroups.33 All reported P values are two-sided. Analysis of the data was performed at GlaxoSmithKline, the sponsor of the study. The authors had access to the primary data, directed the analyses, and made all decisions pertaining to the manuscript and its submission for publication.
Results
Demographics
The trial was initiated in February 1998, and the last couple was enrolled in July 2001. Of the 4034 screened couples, 1385 of the susceptible partners (34.3 percent) were HSV-2¨Cpositive at the time of screening and hence were ineligible, 799 of the source partners (19.8 percent) were not HSV-2¨Cpositive and hence were ineligible, and 352 couples (8.7 percent) declined to take part; hence, 1498 couples (37.1 percent), from 96 sites, proceeded to randomization. Fourteen persons (7 assigned to the valacyclovir group and 7 to the placebo group) elected not to take the study medication, leaving 1484 participating couples. Our analyses were based on data from the 1484 source partners (743 in the valacyclovir group and 741 in the placebo group) who took their assigned study medication. The number of couples at each study center varied from 1 to 141 (median, 8). Of the 1484 participating couples, 803 were in the United States, 118 in Canada, 462 in Europe, 43 in Latin America, and 58 in Australia.
Of the 1484 participating couples, 1159 (78.1 percent) completed the study. Reasons for withdrawal among the remaining 325 couples were based on the source partner's reason and included 82 who withdrew voluntarily (28 assigned to valacyclovir and 54 to placebo), 99 who were lost to follow-up (53 and 46, respectively), 66 whose relationship was dissolved (33 and 33, respectively), 16 who had an adverse event (11 and 5, respectively), 16 for whom there were protocol violations (8 and 8, respectively), 13 who decided to attempt pregnancy (6 and 7, respectively), 9 who reported frequent recurrences while taking the study medication (1 and 8, respectively), and 24 who withdrew for other reasons (18 and 6, respectively). The total number of withdrawals and the reasons for withdrawal were similar for the couples whose source partner was assigned to take valacyclovir (21 percent) and those whose source partner was assigned to take placebo (23 percent). However, voluntary withdrawal was more frequent among source partners who were randomly assigned to placebo than among those who were randomly assigned to valacyclovir (54 vs. 28, P=0.003), probably because of the frequent recurrences among the placebo-treated source partners.
Among the 1484 HSV-2¨Csusceptible subjects, 488 (32.9 percent) were the female partners of men with HSV-2 infection (Table 1). Of these women, 383 were seropositive for HSV-1 (78.5 percent). Of the 996 susceptible partners who were men, 641 were HSV-1¨Cseropositive (64.4 percent).
Table 1. Demographic and Clinical Characteristics of the HSV-2¨CInfected (Source) Partners and the HSV-2¨CSeronegative Susceptible Partners, According to the Source Partner's Treatment Assignment.
Compliance with the medication regimen was high. Overall, 1042 of the 1484 source partners (70.2 percent) reported taking at least 95 percent of the prescribed doses.
Acquisition of HSV Infection and Disease
The end-points committee reviewed data from 71 susceptible partners in whom genitourinary signs and symptoms compatible with new genital herpes developed during the course of the study. Twenty had clinical and laboratory evidence of genital HSV-2 infection associated with these symptoms: in 15 (2 taking valacyclovir and 13 taking placebo) HSV-2 seroconversion (with or without detection of virus) confirmed the diagnosis, and in 5 (2 valacyclovir and 3 placebo) the diagnosis was confirmed by viral culture or HSV PCR only. Of the remaining 51 susceptible partners with genitourinary symptoms, 3 (2 valacyclovir and 1 placebo) had seroconversion to HSV-2 positivity during the study; however, the seroconversion predated the reported symptoms, and hence the new infection was believed to be asymptomatic. In the remaining 48 susceptible partners with genitourinary symptoms, the symptoms were rejected as end points because none of the susceptible partners had laboratory evidence of genital herpes. The source partners of these 48 subjects were almost equally divided between the placebo group (with 25) and the valacyclovir group (with 23). Of the 1413 susceptible partners who did not have symptoms, 18 had seroconversion to HSV-2 and 4 had seroconversion to HSV-1. Thus, a total of 41 HSV-2 infections and 4 HSV-1 infections were detected during the study period. Of these 45 documented infections, 14 were acquired by the sexual partners of subjects who were taking valacyclovir, as compared with 31 partners of subjects who were taking placebo (Table 2 and Figure 1A).
Table 2. Acquisition of HSV Infection among the Susceptible Partners, According to the Source Partner's Treatment Assignment.
Figure 1. Kaplan¨CMeier Plots of Time to Acquisition of HSV Infection among Susceptible Sexual Partners of Persons with Genital HSV-2 Infection, According to the Source Partner's Treatment Group.
Panel A shows the time to acquisition of either HSV-1 or HSV-2 infection among susceptible partners. The hazard ratio for those whose source partner was taking valacyclovir as compared with placebo was 0.45 (95 percent confidence interval, 0.24 to 0.84; P=0.01). Panel B shows the time to the development of symptoms of genital HSV-2 infection among susceptible partners. The hazard ratio for those whose source partner was taking valacyclovir was 0.25 (95 percent confidence interval, 0.08 to 0.75; P=0.008). Panel C shows the time to acquisition of HSV-2 infection among susceptible partners. The hazard ratio for those whose partner was taking valacyclovir was 0.52 (95 percent confidence interval, 0.27 to 0.99; P=0.04). Panel D shows the time to HSV-2 infection among susceptible partners, according to sex.
Of the 41 HSV-2 infections, 20 were associated with symptomatic new genital herpes (the primary end point of the study) and 21 with seroconversion only (Table 2). Of the 20 symptomatic acquisitions of HSV-2, 16 occurred among the 741 partners of placebo recipients (2.2 percent), as compared with 4 among the 743 partners of valacyclovir recipients (0.5 percent) (relative risk, 0.25; 95 percent confidence interval, 0.08 to 0.74; P=0.01). The time to development of a symptomatic first episode of genital herpes was significantly longer among the partners of valacyclovir recipients than among the partners of placebo recipients (Figure 1B). When we evaluated all 41 cases of HSV-2 acquisition, we found that HSV-2 had been acquired by 27 of the susceptible partners of placebo recipients (3.6 percent) as compared with 14 of the susceptible partners of valacyclovir recipients (1.9 percent) (hazard ratio, 0.52; 95 percent confidence interval, 0.27 to 0.99; P=0.04) (Table 2 and Figure 1C). More female partners than male partners of placebo-treated subjects acquired HSV-2 infection (7.4 percent vs. 1.8 percent) (Table 3 and Figure 1D). Time-to-event analysis revealed no evidence of a significant difference in treatment effect between susceptible female and male partners (P=0.73 by the interaction test) (Figure 1D).
Table 3. Rates of Transmission of HSV-2 Infection to Susceptible Partners, According to Risk Stratum.
HSV Reactivation and Shedding among Source Partners
Among the 741 source partners assigned to take placebo, 573 reported a genital recurrence during the study (77.3 percent), as compared with 288 of the 743 assigned to take valacyclovir (38.8 percent) (P<0.001). Valacyclovir significantly prolonged the time to a first recurrence (hazard ratio, 0.30; 95 percent confidence interval, 0.26 to 0.35; P<0.001). The mean rate of recurrence was 0.40 per month among the source partners taking placebo as compared with 0.11 per month among those taking valacyclovir (P<0.001).
The 89 source partners participating in the shedding substudy (68 women and 21 men) collected daily samples of genital secretions for a median of 58 days. Overall, HSV was detected by PCR on 2.9 percent of the days among the 39 source partners taking valacyclovir as compared with 10.8 percent of the days among the 50 source partners taking placebo (P<0.001). Shedding was detected in 19 of 39 valacyclovir-treated partners (48.7 percent), as compared with 41 of 50 placebo-treated partners (82.0 percent) (relative risk, 0.60; 95 percent confidence interval, 0.43 to 0.83; P=0.002). The difference in shedding was seen in both men and women. In only 3 of 39 valacyclovir-treated source partners (7.7 percent) was HSV DNA detected on at least 10 percent of the days, as compared with 25 of 50 placebo-treated source partners (50.0 percent, P<0.001) (Figure 2A). Shedding occurred on 3.3 percent and 0.9 percent of the days among the valacyclovir-treated women and men, respectively, as compared with 11.4 percent and 9.2 percent of the days among placebo-treated women and men. The median number of genome copies of HSV DNA from positive mucosal-swab specimens was 1x103.1 in the valacyclovir group and 1x105.4 in the placebo group (P<0.001) (Figure 2B).
Figure 2. Frequency and Titer of HSV-2 Shedding among Valacyclovir-Treated as Compared with Placebo-Treated Source Partners.
Panel A shows the frequency of shedding of HSV-2 in the genital tract among source partners taking valacyclovir as compared with those taking placebo (P<0.001 by the stratified Wilcoxon test). Panel B shows the number of copies of HSV-2 per milliliter of genital-swab sample during episodes of shedding among source partners taking valacyclovir as compared with those taking placebo (P<0.001 by the stratified Wilcoxon test).
Sexual Activity, Condom Use, and Covariates of Transmission
The median number of sexual contacts per couple during the study was 49 in the valacyclovir group and 46 in the placebo group (range, 0 to 482). The frequency of genital HSV-2 acquisition increased with the reported frequency of sexual activity and was 0.35 per 1000 sexual contacts among the susceptible partners of valacyclovir recipients, as compared with 0.68 per 1000 sexual contacts among the susceptible partners of placebo recipients. The respective rates of acquisition among susceptible women were 0.60 and 1.27 per 1000 sexual contacts and, among susceptible men, 0.23 and 0.35 per 1000 sexual contacts.
Despite counseling, 37 percent of the couples reported at each monthly visit that they never used condoms for vaginal or anal intercourse at all during the study, 20 percent reported that they used condoms more than 90 percent of the time, and 43 percent reported that they used them between 1 and 90 percent of the time. Although rates of transmission of HSV-2 were lower in the valacyclovir group than in the placebo group for all levels of condom use (Table 3), there was considerable overlap between the groups in the rates of acquisition (see Supplementary Appendix 1, available with the full text of this article at www.nejm.org).
Exploratory covariate analyses were performed for both clinical and overall HSV-2 acquisition. Condom use was defined as a time-dependent covariate. In these multivariate analyses, factors found to influence the risk of HSV-2 transmission significantly were female sex of the susceptible partner, greater number of sexual contacts, and shorter duration of genital herpes in the source partner (Table 3 and Table 4). There was no evidence that valacyclovir had a reduced therapeutic effect when efficacy was examined among subgroups defined by these covariates.
Table 4. Covariate Analyses of Factors Influencing the Transmission of Genital Herpes.
Adverse Effects and Susceptibility of Isolates from Cases of Acquisition
The frequency of adverse effects was similar in the placebo and valacyclovir groups and was similar to those reported in studies of valacyclovir in immunocompetent persons with genital herpes.23,25,29 No serious adverse events were considered by the investigators to be related to use of the study medication. HSV-2 isolates were available for sensitivity testing from 11 of the 20 cases of symptomatic new infection. All 11 isolates were sensitive to acyclovir, with plaque-neutralization titers of less than 0.2 ¦Ìg per milliliter.30
Discussion
Our study demonstrates that oral valacyclovir taken by immunocompetent persons with recurrent genital HSV-2 infection significantly reduces the rates of HSV reactivation, subclinical shedding, and transmission of genital herpes to a susceptible partner. A 500-mg dose of valacyclovir taken once daily reduced the risks of acquisition of symptomatic genital herpes and acquisition of HSV-2 infection overall by susceptible, HSV-2¨Cseronegative heterosexual partners. The results of the trial demonstrate the effectiveness of treating the source partner with an antiviral agent to reduce the risk of transmission of a sexually transmitted viral disease. The results were in addition to any effects that may have been attributable to counseling or safer-sex practices used by the study population.
People with genital herpes and their sexual partners consider the transmission of this infection their chief concern.17 Adding to this concern are data showing that HSV-2¨Cseropositive persons have an increased risk of infection with the human immunodeficiency virus11,12,13,14,34 and that new HSV-2 infection during late pregnancy poses a high risk of transmission of HSV-2 to the neonate.35 Condoms are partially effective in reducing HSV-2 transmission and, along with abstinence during outbreaks, should continue to be recommended.36 Our trial was conducted among couples who received monthly counseling about the use of condoms for reducing the risk of transmission of HSV-2 infection and other sexually transmitted infections and who were offered free condoms. Yet, 37 percent of the couples reported no condom use during the trial. Covariate analyses accounting for reported condom use indicated that valacyclovir use continued to be associated with reduced rates of transmission. The lowest observed rates of transmission were among couples who reported that they almost always used condoms and in whom the source partner was taking valacyclovir. However, our study does not allow us to define what levels of condom use in combination with valacyclovir therapy provide optimal or suboptimal protection.
We studied persons with recurrent genital herpes who were already candidates for antiviral suppression. Prevention of transmission of HSV infection is an added benefit to the relief of clinically symptomatic disease in such persons. According to the overall rate of HSV-2 acquisition that we observed and the 48 percent reduction in risk with valacyclovir, one would expect to treat 38 persons with recurrent genital herpes for a year to prevent one case of HSV-2 infection in a susceptible partner. However, this number varies according to the sex of the susceptible partner, frequency of condom use, duration of the relationship, and other variables that influence the likelihood of transmission. Thus, in our study, the annualized number needed to treat is 11 for couples in which the susceptible woman's partner will not use condoms and 24 for couples with the highest level of sexual activity.
The frequency of acquisition of HSV-2 infection in our trial was lower than in trials of HSV-2 acquisition conducted in observational cohorts and other discordant partnerships, probably because of the low biologic risk of infection among long-standing couples, the high proportion of susceptible male participants, and the extensive counseling we performed.7,15,16,37,38 If one used the annualized incidence of 11.4 percent, derived from a recent trial of vaccination to prevent HSV infection in seronegative subjects,16 the overall number of persons needed to treat would be 18 to prevent one transmission. If one used data from an observational cohort study of susceptible pregnant women with HSV-2¨Cseropositive partners, the number needed to treat would be 11.37 The lower rate of transmission from HSV-2¨Cinfected women to men makes this figure two to three times higher in discordant couples in which the susceptible partner is female.
To what extent can we extrapolate both the biologic and cost-effectiveness aspects of the data in this study to other settings? It is likely that the transmission effects we found are applicable to nonmonogamous heterosexual couples. Valacyclovir is effective in suppressing genital herpes in men who have sex with men.39 However, as shown in the trial, sexual transmission is influenced by sexual behavior and biologic factors. Most instances of HSV-2 transmission occur with source partners who do not have a history of genital herpes,5,15,38 and few studies describing daily antiviral medication in such persons are available. Additional studies to evaluate whether suppressive therapy will prevent transmission among couples with a source partner with subclinical HSV-2 infection, couples in whom the susceptible partner is immunocompromised, and homosexual couples should be undertaken. Studies in which the susceptible partner is pregnant are of special importance because of the high risk of acquisition of HSV-1 or HSV-2 infection in this setting. The few cases of asymptomatic HSV-1 acquisition in this study were not sufficient to allow us to determine whether valacyclovir would reduce the risk of HSV-1 transmission.
Because the observed reduction in the rate of transmission of genital herpes with valacyclovir is clinically relevant but not complete, it is important that disclosure of genital herpes to the susceptible partner and the practice of safer sex continue, since both may reduce the risk of transmission of genital herpes.
Supported by GlaxoSmithKline Research and Development and a grant (AI-30731) from the National Institutes of Health.
Dr. Corey reports supervision of laboratories that perform work on a contract basis for GlaxoSmithKline, Novartis, and 3M. Dr. Wald reports having received consultation fees from Biovail, Eli Lilly, and Novartis and lecture fees from GlaxoSmithKline. Dr. Patel reports having received consultation and lecture fees from GlaxoSmithKline and Novartis, consultation fees from Eli Lilly and 3M, and grant support from GlaxoSmithKline and reports holding equity in GlaxoSmithKline. Dr. Sacks reports having received consultation and lecture fees from GlaxoSmithKline and Novartis and holding equity in Viridae Clinical Sciences. Dr. Tyring reports having received consultation and lecture fees and grant support from GlaxoSmithKline. Dr. Warren reports having received consultation and lecture fees from GlaxoSmithKline. Dr. Douglas reports having received lecture fees from GlaxoSmithKline. Dr. Paavonen reports having received speakers' honorariums from GlaxoSmithKline. Dr. Morrow reports having received consultation fees from Bio-Rad, Focus, GlaxoSmithKline, and Novartis; lecture fees from Quest Diagnostics and Quadrant Health; and grant support from Trinity Bio-Tech. Dr. Beutner reports having received consultation and lecture fees from GlaxoSmithKline, Eli Lilly, and 3M. Dr. Mertz reports having received consultation fees from GlaxoSmithKline and Eli Lilly, lecture fees from GlaxoSmithKline, and grant support from 3M.
This article is dedicated to the memory of Stephen L. Sacks, M.D., whose research on genital herpes contributed substantially to our findings.
We are indebted to the 1498 couples, the investigators, and the study staff for their tremendous contribution to this demanding trial; to Julia Harris and Judith Zeh, statisticians, for their contributions to the analyses and study design, respectively; to Stacy Selke for her role in management of the data; to Zane Brown and Dorothea Griffiths for their work on the End-Points Committee; and to Alison Webster, Robert Deeter, and Karen Coates, all of GlaxoSmithKline, for their assistance.
* Members of the Valacyclovir Herpes Simplex Virus (HSV) Transmission Study Group are listed in the Appendix.
Source Information
From the Departments of Medicine (L.C., A.W.), Laboratory Medicine (L.C., R.A.M.), and Epidemiology (A.W.), University of Washington, Seattle; the Program in Infectious Diseases, Fred Hutchinson Cancer Research Center, Seattle (L.C.); the Department of Genitourinary Medicine, Royal South Hants Hospital, Southampton, United Kingdom (R.P.); Viridae Clinical Sciences and University of British Columbia, Vancouver, Canada (S.L.S.); the University of Texas Medical Branch, Galveston (S.K.T.); Westover Heights Clinic, Portland, Oreg. (T.W.); the Disease Control Service, Denver Department of Public Health, Denver (J.M.D.); the Department of Obstetrics and Gynecology, University of Helsinki, Helsinki, Finland (J.P.); Dow Pharmaceutical Sciences and Department of Dermatology, University of California, San Francisco (K.R.B.); the Department of Clinical Pharmacology, Smolensk State Medical Academy, Smolensk, Russia (L.S.S.); the Department of Medicine, University of New Mexico, Albuquerque (G.M.); and the Departments of Biomedical Data Sciences (O.N.K.) and Antiviral Clinical Research (H.A.W., D.T., M.V.-C.), GlaxoSmithKline Research and Development, Greenford, United Kingdom.
Address reprint requests to Dr. Corey at the Program in Infectious Diseases, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., Rm. D3-100, P.O. Box 19024, Seattle, WA 98109, or at lcorey@u.washington.edu.
References
Corey L, Wald A. Genital herpes. In: Holmes KK, M?rdh P-A, Sparling PF, et al., ed. Sexually transmitted diseases. 3rd ed. New York: McGraw-Hill, 1999:285-312.
Ashley R, Wald A. Genital herpes: review of the epidemic and potential uses of type-specific serology. Clin Microbiol Rev 1999;12:1-8.
Benedetti J, Corey L, Ashley R. Recurrence rates of genital herpes after symptomatic first-episode infection. Ann Intern Med 1994;121:847-854.
Wald A, Zeh J, Selke S, Ashley RL, Corey L. Virologic characteristics of subclinical and symptomatic genital herpes infections. N Engl J Med 1995;333:770-775.
Langenberg AGM, Corey L, Ashley RL, Leong WP, Straus SE. A prospective study of new infections with herpes simplex virus type 1 and type 2. N Engl J Med 1999;341:1432-1438.
Rooney JF, Felser JM, Ostrove JM, Straus SE. Acquisition of genital herpes from an asymptomatic sexual partner. N Engl J Med 1986;314:1561-1564.
Mertz GJ, Coombs RW, Ashley RL, et al. Transmission of genital herpes in couples with one symptomatic and one asymptomatic partner: a prospective study. J Infect Dis 1988;157:1169-1177.
Mertz GJ, Schmidt O, Jourden JL, et al. Frequency of acquisition of first-episode genital infection with herpes simplex virus from symptomatic and asymptomatic source contacts. Sex Transm Dis 1985;12:33-39.
Fleming DT, McQuillan GM, Johnson RE, et al. Herpes simplex virus type 2 in the United States, 1976 to 1994. N Engl J Med 1997;337:1105-1111.
Armstrong G, Schillinger J, Markowitz L, et al. Incidence of herpes simplex virus type 2 infection in the United States. Am J Epidemiol 2001;153:912-920.
Beyrer C, Jitwatcharanan K, Natpratan C, et al. Molecular methods for the diagnosis of genital ulcer disease in a sexually transmitted disease clinic population in northern Thailand: predominance of herpes simplex virus infection. J Infect Dis 1998;178:243-246.
Chen CY, Ballard RC, Beck-Sague CM, et al. Human immunodeficiency virus infection and genital ulcer disease in South Africa: the herpetic connection. Sex Transm Dis 2000;27:21-29.
Mwansasu A, Mwakagile D, Haarr L, Langeland N. Detection of HSV-2 in genital ulcers from STD patients in Dar es Salaam, Tanzania. J Clin Virol 2002;24:183-192.
Wald A, Link K. Risk of human immunodeficiency virus infection in herpes simplex virus type-2 seropositive persons: a meta-analysis. J Infect Dis 2002;185:45-52.
Corey L, Langenberg AGM, Ashley R, et al. Recombinant glycoprotein vaccine for the prevention of genital HSV-2 infection: two randomized, controlled trials. JAMA 1999;282:331-340.
Stanberry LR, Spruance SL, Cunningham AL, et al. Glycoprotein-D-adjuvant vaccine to prevent genital herpes. N Engl J Med 2002;347:1652-1661.
Carney O, Ross E, Bunker C, Ikkos G, Mindel A. A prospective study of the psychological impact on patients with a first episode of genital herpes. Genitourin Med 1994;70:40-45.
Douglas JM, Critchlow C, Benedetti J, et al. A double-blind study of oral acyclovir for suppression of recurrences of genital herpes simplex virus infection. N Engl J Med 1984;310:1551-1556.
Goldberg LH, Kaufman R, Kurtz TO, et al. Long-term suppression of recurrent genital herpes with acyclovir: a 5-year benchmark. Arch Dermatol 1993;129:582-587.
Wald A, Corey L, Cone R, Hobson A, Davis G, Zeh J. Frequent genital herpes simplex virus 2 shedding in immunocompetent women: effect of acyclovir treatment. J Clin Invest 1997;99:1092-1097.
Wald A, Warrant T, Hu H, et al. Suppression of subclinical shedding of herpes simplex virus type 2 in the genital tract with valaciclovir. In: Program and abstracts of the 38th Interscience Conference on Antimicrobial Agents and Chemotherapy, San Diego, Calif., September 24¨C27, 1998. Washington, D.C.: American Society for Microbiology, 1998:338. abstract.
Sacks SL, Hughes A, Rennie B, Boon R. Famciclovir for suppression of asymptomatic and symptomatic recurrent genital herpes shedding: a randomized double-blind, double-dummy, parallel-group, placebo-controlled trial. In: Program and abstracts of the 37th Interscience Conference on Antimicrobial Agents and Chemotherapy, Toronto, September 28¨COctober 1, 1997. Washington, D.C.: American Society for Microbiology, 1997:227. abstract.
Patel R, Bodsworth NJ, Woolley P, et al. Valaciclovir for the suppression of recurrent genital HSV infection: a placebo controlled study of once daily therapy. Genitourin Med 1997;73:105-109.
Genital herpes: a patient guide to treatment. Chicago: American Medical Association, 1997.
Spruance SL, Tyring SK, DeGregorio B, Miller C, Beutner K. A large-scale, placebo-controlled, dose-ranging trial of peroral valaciclovir for episodic treatment of recurrent herpes genitalis. Arch Intern Med 1996;156:1729-1735.
Wald A, Zeh J, Selke S, et al. Reactivation of genital herpes simplex virus type 2 infection in asymptomatic seropositive persons. N Engl J Med 2000;342:844-850.
Ryncarz AJ, Goddard J, Wald A, Huang ML, Roizman B, Corey L. Development of a high-throughput quantitative assay for detecting herpes simplex virus DNA in clinical samples. J Clin Microbiol 1999;37:1941-1947.
Jerome KR, Huang ML, Wald A, Selke S, Corey L. Quantitative stability of DNA after extended storage of clinical specimens as determined by real-time PCR. J Clin Microbiol 2002;40:2609-2611.
Fife KH, Barbarash RA, Rudolph T, Degregorio B, Roth R. Valaciclovir versus acyclovir in the treatment of first-episode genital herpes infection: results of an international, multicenter, double-blind, randomized clinical trial. Sex Transm Dis 1997;24:481-486.
Bacon TH, Levin JM, Leary J, Sarisky RT, Sutton D. Herpes simplex virus resistance to acyclovir and penciclovir after two decades of antiviral therapy. Clin Microbiol Rev 2003;16:114-128.
Gart JJ. Point and interval estimation of the common odds ratio in the combination of 2x2 tables with fixed marginals. Biometrika 1970;57:471-475.
Shuster JJ. Fixing the number of events in large comparative trials with low event rates: a binomial approach. Control Clin Trials 1993;14:198-208.
Zelen M. The analysis of several 2x2 contingency tables. Biometrika 1971;58:129-137.
Stamm W, Handsfield HH, Rompalo AM, Ashley RL, Roberts PL, Corey L. The association between genital ulcer disease and acquisition of HIV infection in homosexual men. JAMA 1988;260:1429-1433.
Brown ZA, Wald A, Morrow RA, Selke S, Zeh J, Corey L. Effect of serologic status and cesarean delivery on transmission rates of herpes simplex virus from mother to infant. JAMA 2003;289:203-209.
Wald A, Langenberg AGM, Link K, et al. Effect of condoms on reducing the transmission of herpes simplex virus type 2 from men to women. JAMA 2001;285:3100-3106.
Gardella C, Ashley R, Berry S, et al. The risk of acquisition of herpes simplex virus during pregnancy: a prospective couples study. Presented at the Annual Research Meeting of the Infectious Diseases Society for Obstetrics and Gynecology, Quebec City, Canada, August 9¨C11, 2001. abstract.
Wald A, Selke S, Lowens S, et al. Sexual transmission of genital HSV: risk factors in a time-to-event analysis. In: Program and abstracts of STIs at the Millennium: Joint Meeting of the American Sexually Transmitted Diseases Association/Medical Society for the Study of Venereal Diseases, Baltimore, May 3¨C7, 2000. abstract.
Conant MA, Schacker TW, Murphy RL, Gold J, Crutchfield LT, Crooks RJ. Valaciclovir versus aciclovir for herpes simplex virus infection in HIV-infected individuals: two randomized trials. Int J STD AIDS 2002;13:12-21.(Lawrence Corey, M.D., Ann)
Background Nucleoside analogues against herpes simplex virus (HSV) have been shown to suppress shedding of HSV type 2 (HSV-2) on genital mucosal surfaces and may prevent sexual transmission of HSV.
Methods We followed 1484 immunocompetent, heterosexual, monogamous couples: one with clinically symptomatic genital HSV-2 and one susceptible to HSV-2. The partners with HSV-2 infection were randomly assigned to receive either 500 mg of valacyclovir once daily or placebo for eight months. The susceptible partner was evaluated monthly for clinical signs and symptoms of genital herpes. Source partners were followed for recurrences of genital herpes; 89 were enrolled in a substudy of HSV-2 mucosal shedding. Both partners were counseled on safer sex and were offered condoms at each visit. The predefined primary end point was the reduction in transmission of symptomatic genital herpes.
Results Clinically symptomatic HSV-2 infection developed in 4 of 743 susceptible partners who were given valacyclovir, as compared with 16 of 741 who were given placebo (hazard ratio, 0.25; 95 percent confidence interval, 0.08 to 0.75; P=0.008). Overall, acquisition of HSV-2 was observed in 14 of the susceptible partners who received valacyclovir (1.9 percent), as compared with 27 (3.6 percent) who received placebo (hazard ratio, 0.52; 95 percent confidence interval, 0.27 to 0.99; P=0.04). HSV DNA was detected in samples of genital secretions on 2.9 percent of the days among the HSV-2¨Cinfected (source) partners who received valacyclovir, as compared with 10.8 percent of the days among those who received placebo (P<0.001). The mean rates of recurrence were 0.11 per month and 0.40 per month, respectively (P<0.001).
Conclusions Once-daily suppressive therapy with valacyclovir significantly reduces the risk of transmission of genital herpes among heterosexual, HSV-2¨Cdiscordant couples.
Herpes simplex virus type 2 (HSV-2) causes a chronic genital viral infection characterized by high rates of clinical and subclinical reactivation in the genital mucosa and the attendant risk of sexual transmission.1,2,3,4 Both symptomatic and asymptomatic reactivations of HSV infection have been shown to result in sexual transmission.5,6,7,8 Population-based studies in the United States indicate that 22 percent of adults have antibodies to HSV-2 and that an estimated 1.6 million new cases of HSV-2 infection are acquired yearly.9,10 HSV-2 has become the most frequent cause of genital ulcer disease in all regions of the world.11,12,13,14
Transmission of genital herpes to others is the chief concern in persons with known genital herpes.15,16,17 Although antiviral agents have been shown for nearly two decades to reduce the frequency of clinical reactivation of genital herpes,18,19 only more recently has it been shown that daily antiviral therapy also reduces the frequency and amount of HSV that is shed subclinically on genital mucosal surfaces, the principal source of transmitted infections.20,21,22 This reduction in subclinical shedding provided the rationale for our randomized, placebo-controlled trial, which was designed to determine whether once-daily valacyclovir could reduce the risk of sexual transmission of genital herpes.
Methods
Study Population
We enrolled heterosexual couples who were serologically discordant for HSV-2 infection from 96 study sites. The inclusion criteria for the HSV-2¨Cseropositive source partner were an age of 18 years or older, presence of recurrent genital herpes with fewer than 10 episodes per year, and nonuse of any daily antiviral therapy. The inclusion criteria for the susceptible partner were an age of 18 years or older and HSV-2 seronegativity on Western blot analysis. The relationship between the source partner and the susceptible partner was required to be monogamous. Both partners were required to be immunocompetent and in good health and the couple to be using effective contraception.
Study Design
The partners signed separate informed-consent forms that had been approved by local institutional review boards. The partners were seen together at the screening visit, separately at randomization, and at monthly intervals during the eight-month study period. The HSV-2¨Cseropositive partners were randomly assigned, in a 1:1 ratio, to 500 mg of valacyclovir once daily or to matching placebo.23 At each visit, safer sex practices, including the use of condoms during sexual intercourse, were discussed with each partner, and standardized counseling was provided when signs and symptoms of genital herpes were recognized.24 Condoms were provided free of charge to all participants in the trial throughout the study period. For the source partner, adverse experiences and recurrences of genital herpes were recorded on diary cards and reviewed at each clinic visit. The source partners were asked to come to the clinic during recurrences for which episodic therapy with valacyclovir (500 mg twice a day) for five days was offered.25 After the five-day course of valacyclovir had been completed, the source partner resumed taking the randomly assigned medication.
Source partners at four centers were invited to participate in a substudy to define the frequency of reactivation of HSV-2 infection in the genital region. Participants in this substudy were instructed on how to swab the genital secretions every day for two months. Women swabbed the cervicovaginal, vulvar, and perianal regions, and men swabbed the penile skin and perianal area.4,20,21,22,26 The participants placed the swabs in polymerase-chain-reaction (PCR) buffer and delivered them to the clinic at the next scheduled visit.
During monthly visits by the susceptible partner, serum samples were collected for HSV analysis, and diaries were reviewed for notes concerning sexual activity, condom use, and symptoms suggestive of incident genital herpes during the preceding month.5 The susceptible partners were instructed to visit the clinic if they observed symptoms or lesions compatible with genital herpes. Separate swabs of genital secretions were obtained for HSV culture and HSV DNA detection by PCR and were shipped to the central laboratory at the University of Washington.27,28 If new genital herpes was clinically diagnosed, patients were offered treatment with a licensed dose of valacyclovir.29
Study End Points
Acquisition of HSV-2 infection was defined as the isolation of HSV-2 in culture, the detection of HSV-2 DNA, or HSV-2 seroconversion in the susceptible partner during the course of the trial.2,5,8,15,16 Clinically symptomatic genital herpes was defined according to the presence of clinical signs and symptoms and was confirmed by isolation of HSV-2 in culture, detection of HSV-2 DNA by PCR, or HSV-2 seroconversion. An end-points committee, whose members were blinded to the treatment assignment, reviewed all cases of genital herpes clinically diagnosed during the study. This committee also reviewed all cases in which the susceptible partner had an abnormal genital symptom or sign during the study, as well as all cases of genital herpes confirmed by laboratory analysis.
Laboratory Analyses
All serum was sent to the central laboratory. Serum samples obtained at the time of screening, at the time of randomization, and at one month and eight months were run in parallel on Western blots. Seroconversion was defined according to previously published criteria ¡ª namely, the development of one to four new bands, including bands corresponding to HSV-2 glycoprotein G type 2 (gG2) or to HSV type 1 (HSV-1) glycoproteins, such as glycoprotein G type 1 (gG1).5,8,15 Cultures and PCR analyses for HSV were performed as previously described.4,26,27,28 All isolates from susceptible partners who acquired HSV-2 were tested for their susceptibility to acyclovir by the plaque-reduction assay.30
Statistical Analysis
The predefined primary end point was a laboratory-confirmed, clinically symptomatic first episode of genital HSV-2 infection in the susceptible partner. Secondary end points included the time to overall HSV-2 acquisition (i.e., the occurrence of the primary end point, HSV-2 seroconversion in the susceptible partner, or both) and the time to a first recurrence of genital HSV-2 in the source partner. A 3 percent rate of clinically symptomatic genital herpes (annualized rate, 5 percent) was assumed for placebo.15 Because this study was designed to detect a 75 percent difference between valacyclovir and placebo in the rates of clinically symptomatic disease, we estimated that 28 confirmed cases of genital HSV-2 infection were required for 90 percent power with a two-tailed test of proportions at the 5 percent significance level.31 It was estimated that random assignment of 750 couples to each treatment group would achieve these assumptions. Randomization was performed at a central site in blocks of 10 to ensure balance between the groups. Randomization was stratified according to the sex and HSV-1 status of the susceptible partners.
The two study groups were compared with respect to the primary end point with use of the stratified version of Fisher's exact test.32 Analyses included data from all the subjects who had been randomly assigned to a study group and who took at least one dose of medication. No interim analyses were planned or conducted. The study groups were compared with respect to time-to-event end points with use of the log-rank test, with stratification according to the susceptible partner's sex and HSV-1 status on screening. Hazard ratios were calculated by means of the Cox proportional-hazards model, with covariates defined according to stratum and treatment. Data for subjects who did not reach an end point were censored as event-free periods ending on the last day that the absence of the end point was confirmed. Interaction tests were used to determine whether there was evidence of a differential effect of valacyclovir treatment across subgroups.33 All reported P values are two-sided. Analysis of the data was performed at GlaxoSmithKline, the sponsor of the study. The authors had access to the primary data, directed the analyses, and made all decisions pertaining to the manuscript and its submission for publication.
Results
Demographics
The trial was initiated in February 1998, and the last couple was enrolled in July 2001. Of the 4034 screened couples, 1385 of the susceptible partners (34.3 percent) were HSV-2¨Cpositive at the time of screening and hence were ineligible, 799 of the source partners (19.8 percent) were not HSV-2¨Cpositive and hence were ineligible, and 352 couples (8.7 percent) declined to take part; hence, 1498 couples (37.1 percent), from 96 sites, proceeded to randomization. Fourteen persons (7 assigned to the valacyclovir group and 7 to the placebo group) elected not to take the study medication, leaving 1484 participating couples. Our analyses were based on data from the 1484 source partners (743 in the valacyclovir group and 741 in the placebo group) who took their assigned study medication. The number of couples at each study center varied from 1 to 141 (median, 8). Of the 1484 participating couples, 803 were in the United States, 118 in Canada, 462 in Europe, 43 in Latin America, and 58 in Australia.
Of the 1484 participating couples, 1159 (78.1 percent) completed the study. Reasons for withdrawal among the remaining 325 couples were based on the source partner's reason and included 82 who withdrew voluntarily (28 assigned to valacyclovir and 54 to placebo), 99 who were lost to follow-up (53 and 46, respectively), 66 whose relationship was dissolved (33 and 33, respectively), 16 who had an adverse event (11 and 5, respectively), 16 for whom there were protocol violations (8 and 8, respectively), 13 who decided to attempt pregnancy (6 and 7, respectively), 9 who reported frequent recurrences while taking the study medication (1 and 8, respectively), and 24 who withdrew for other reasons (18 and 6, respectively). The total number of withdrawals and the reasons for withdrawal were similar for the couples whose source partner was assigned to take valacyclovir (21 percent) and those whose source partner was assigned to take placebo (23 percent). However, voluntary withdrawal was more frequent among source partners who were randomly assigned to placebo than among those who were randomly assigned to valacyclovir (54 vs. 28, P=0.003), probably because of the frequent recurrences among the placebo-treated source partners.
Among the 1484 HSV-2¨Csusceptible subjects, 488 (32.9 percent) were the female partners of men with HSV-2 infection (Table 1). Of these women, 383 were seropositive for HSV-1 (78.5 percent). Of the 996 susceptible partners who were men, 641 were HSV-1¨Cseropositive (64.4 percent).
Table 1. Demographic and Clinical Characteristics of the HSV-2¨CInfected (Source) Partners and the HSV-2¨CSeronegative Susceptible Partners, According to the Source Partner's Treatment Assignment.
Compliance with the medication regimen was high. Overall, 1042 of the 1484 source partners (70.2 percent) reported taking at least 95 percent of the prescribed doses.
Acquisition of HSV Infection and Disease
The end-points committee reviewed data from 71 susceptible partners in whom genitourinary signs and symptoms compatible with new genital herpes developed during the course of the study. Twenty had clinical and laboratory evidence of genital HSV-2 infection associated with these symptoms: in 15 (2 taking valacyclovir and 13 taking placebo) HSV-2 seroconversion (with or without detection of virus) confirmed the diagnosis, and in 5 (2 valacyclovir and 3 placebo) the diagnosis was confirmed by viral culture or HSV PCR only. Of the remaining 51 susceptible partners with genitourinary symptoms, 3 (2 valacyclovir and 1 placebo) had seroconversion to HSV-2 positivity during the study; however, the seroconversion predated the reported symptoms, and hence the new infection was believed to be asymptomatic. In the remaining 48 susceptible partners with genitourinary symptoms, the symptoms were rejected as end points because none of the susceptible partners had laboratory evidence of genital herpes. The source partners of these 48 subjects were almost equally divided between the placebo group (with 25) and the valacyclovir group (with 23). Of the 1413 susceptible partners who did not have symptoms, 18 had seroconversion to HSV-2 and 4 had seroconversion to HSV-1. Thus, a total of 41 HSV-2 infections and 4 HSV-1 infections were detected during the study period. Of these 45 documented infections, 14 were acquired by the sexual partners of subjects who were taking valacyclovir, as compared with 31 partners of subjects who were taking placebo (Table 2 and Figure 1A).
Table 2. Acquisition of HSV Infection among the Susceptible Partners, According to the Source Partner's Treatment Assignment.
Figure 1. Kaplan¨CMeier Plots of Time to Acquisition of HSV Infection among Susceptible Sexual Partners of Persons with Genital HSV-2 Infection, According to the Source Partner's Treatment Group.
Panel A shows the time to acquisition of either HSV-1 or HSV-2 infection among susceptible partners. The hazard ratio for those whose source partner was taking valacyclovir as compared with placebo was 0.45 (95 percent confidence interval, 0.24 to 0.84; P=0.01). Panel B shows the time to the development of symptoms of genital HSV-2 infection among susceptible partners. The hazard ratio for those whose source partner was taking valacyclovir was 0.25 (95 percent confidence interval, 0.08 to 0.75; P=0.008). Panel C shows the time to acquisition of HSV-2 infection among susceptible partners. The hazard ratio for those whose partner was taking valacyclovir was 0.52 (95 percent confidence interval, 0.27 to 0.99; P=0.04). Panel D shows the time to HSV-2 infection among susceptible partners, according to sex.
Of the 41 HSV-2 infections, 20 were associated with symptomatic new genital herpes (the primary end point of the study) and 21 with seroconversion only (Table 2). Of the 20 symptomatic acquisitions of HSV-2, 16 occurred among the 741 partners of placebo recipients (2.2 percent), as compared with 4 among the 743 partners of valacyclovir recipients (0.5 percent) (relative risk, 0.25; 95 percent confidence interval, 0.08 to 0.74; P=0.01). The time to development of a symptomatic first episode of genital herpes was significantly longer among the partners of valacyclovir recipients than among the partners of placebo recipients (Figure 1B). When we evaluated all 41 cases of HSV-2 acquisition, we found that HSV-2 had been acquired by 27 of the susceptible partners of placebo recipients (3.6 percent) as compared with 14 of the susceptible partners of valacyclovir recipients (1.9 percent) (hazard ratio, 0.52; 95 percent confidence interval, 0.27 to 0.99; P=0.04) (Table 2 and Figure 1C). More female partners than male partners of placebo-treated subjects acquired HSV-2 infection (7.4 percent vs. 1.8 percent) (Table 3 and Figure 1D). Time-to-event analysis revealed no evidence of a significant difference in treatment effect between susceptible female and male partners (P=0.73 by the interaction test) (Figure 1D).
Table 3. Rates of Transmission of HSV-2 Infection to Susceptible Partners, According to Risk Stratum.
HSV Reactivation and Shedding among Source Partners
Among the 741 source partners assigned to take placebo, 573 reported a genital recurrence during the study (77.3 percent), as compared with 288 of the 743 assigned to take valacyclovir (38.8 percent) (P<0.001). Valacyclovir significantly prolonged the time to a first recurrence (hazard ratio, 0.30; 95 percent confidence interval, 0.26 to 0.35; P<0.001). The mean rate of recurrence was 0.40 per month among the source partners taking placebo as compared with 0.11 per month among those taking valacyclovir (P<0.001).
The 89 source partners participating in the shedding substudy (68 women and 21 men) collected daily samples of genital secretions for a median of 58 days. Overall, HSV was detected by PCR on 2.9 percent of the days among the 39 source partners taking valacyclovir as compared with 10.8 percent of the days among the 50 source partners taking placebo (P<0.001). Shedding was detected in 19 of 39 valacyclovir-treated partners (48.7 percent), as compared with 41 of 50 placebo-treated partners (82.0 percent) (relative risk, 0.60; 95 percent confidence interval, 0.43 to 0.83; P=0.002). The difference in shedding was seen in both men and women. In only 3 of 39 valacyclovir-treated source partners (7.7 percent) was HSV DNA detected on at least 10 percent of the days, as compared with 25 of 50 placebo-treated source partners (50.0 percent, P<0.001) (Figure 2A). Shedding occurred on 3.3 percent and 0.9 percent of the days among the valacyclovir-treated women and men, respectively, as compared with 11.4 percent and 9.2 percent of the days among placebo-treated women and men. The median number of genome copies of HSV DNA from positive mucosal-swab specimens was 1x103.1 in the valacyclovir group and 1x105.4 in the placebo group (P<0.001) (Figure 2B).
Figure 2. Frequency and Titer of HSV-2 Shedding among Valacyclovir-Treated as Compared with Placebo-Treated Source Partners.
Panel A shows the frequency of shedding of HSV-2 in the genital tract among source partners taking valacyclovir as compared with those taking placebo (P<0.001 by the stratified Wilcoxon test). Panel B shows the number of copies of HSV-2 per milliliter of genital-swab sample during episodes of shedding among source partners taking valacyclovir as compared with those taking placebo (P<0.001 by the stratified Wilcoxon test).
Sexual Activity, Condom Use, and Covariates of Transmission
The median number of sexual contacts per couple during the study was 49 in the valacyclovir group and 46 in the placebo group (range, 0 to 482). The frequency of genital HSV-2 acquisition increased with the reported frequency of sexual activity and was 0.35 per 1000 sexual contacts among the susceptible partners of valacyclovir recipients, as compared with 0.68 per 1000 sexual contacts among the susceptible partners of placebo recipients. The respective rates of acquisition among susceptible women were 0.60 and 1.27 per 1000 sexual contacts and, among susceptible men, 0.23 and 0.35 per 1000 sexual contacts.
Despite counseling, 37 percent of the couples reported at each monthly visit that they never used condoms for vaginal or anal intercourse at all during the study, 20 percent reported that they used condoms more than 90 percent of the time, and 43 percent reported that they used them between 1 and 90 percent of the time. Although rates of transmission of HSV-2 were lower in the valacyclovir group than in the placebo group for all levels of condom use (Table 3), there was considerable overlap between the groups in the rates of acquisition (see Supplementary Appendix 1, available with the full text of this article at www.nejm.org).
Exploratory covariate analyses were performed for both clinical and overall HSV-2 acquisition. Condom use was defined as a time-dependent covariate. In these multivariate analyses, factors found to influence the risk of HSV-2 transmission significantly were female sex of the susceptible partner, greater number of sexual contacts, and shorter duration of genital herpes in the source partner (Table 3 and Table 4). There was no evidence that valacyclovir had a reduced therapeutic effect when efficacy was examined among subgroups defined by these covariates.
Table 4. Covariate Analyses of Factors Influencing the Transmission of Genital Herpes.
Adverse Effects and Susceptibility of Isolates from Cases of Acquisition
The frequency of adverse effects was similar in the placebo and valacyclovir groups and was similar to those reported in studies of valacyclovir in immunocompetent persons with genital herpes.23,25,29 No serious adverse events were considered by the investigators to be related to use of the study medication. HSV-2 isolates were available for sensitivity testing from 11 of the 20 cases of symptomatic new infection. All 11 isolates were sensitive to acyclovir, with plaque-neutralization titers of less than 0.2 ¦Ìg per milliliter.30
Discussion
Our study demonstrates that oral valacyclovir taken by immunocompetent persons with recurrent genital HSV-2 infection significantly reduces the rates of HSV reactivation, subclinical shedding, and transmission of genital herpes to a susceptible partner. A 500-mg dose of valacyclovir taken once daily reduced the risks of acquisition of symptomatic genital herpes and acquisition of HSV-2 infection overall by susceptible, HSV-2¨Cseronegative heterosexual partners. The results of the trial demonstrate the effectiveness of treating the source partner with an antiviral agent to reduce the risk of transmission of a sexually transmitted viral disease. The results were in addition to any effects that may have been attributable to counseling or safer-sex practices used by the study population.
People with genital herpes and their sexual partners consider the transmission of this infection their chief concern.17 Adding to this concern are data showing that HSV-2¨Cseropositive persons have an increased risk of infection with the human immunodeficiency virus11,12,13,14,34 and that new HSV-2 infection during late pregnancy poses a high risk of transmission of HSV-2 to the neonate.35 Condoms are partially effective in reducing HSV-2 transmission and, along with abstinence during outbreaks, should continue to be recommended.36 Our trial was conducted among couples who received monthly counseling about the use of condoms for reducing the risk of transmission of HSV-2 infection and other sexually transmitted infections and who were offered free condoms. Yet, 37 percent of the couples reported no condom use during the trial. Covariate analyses accounting for reported condom use indicated that valacyclovir use continued to be associated with reduced rates of transmission. The lowest observed rates of transmission were among couples who reported that they almost always used condoms and in whom the source partner was taking valacyclovir. However, our study does not allow us to define what levels of condom use in combination with valacyclovir therapy provide optimal or suboptimal protection.
We studied persons with recurrent genital herpes who were already candidates for antiviral suppression. Prevention of transmission of HSV infection is an added benefit to the relief of clinically symptomatic disease in such persons. According to the overall rate of HSV-2 acquisition that we observed and the 48 percent reduction in risk with valacyclovir, one would expect to treat 38 persons with recurrent genital herpes for a year to prevent one case of HSV-2 infection in a susceptible partner. However, this number varies according to the sex of the susceptible partner, frequency of condom use, duration of the relationship, and other variables that influence the likelihood of transmission. Thus, in our study, the annualized number needed to treat is 11 for couples in which the susceptible woman's partner will not use condoms and 24 for couples with the highest level of sexual activity.
The frequency of acquisition of HSV-2 infection in our trial was lower than in trials of HSV-2 acquisition conducted in observational cohorts and other discordant partnerships, probably because of the low biologic risk of infection among long-standing couples, the high proportion of susceptible male participants, and the extensive counseling we performed.7,15,16,37,38 If one used the annualized incidence of 11.4 percent, derived from a recent trial of vaccination to prevent HSV infection in seronegative subjects,16 the overall number of persons needed to treat would be 18 to prevent one transmission. If one used data from an observational cohort study of susceptible pregnant women with HSV-2¨Cseropositive partners, the number needed to treat would be 11.37 The lower rate of transmission from HSV-2¨Cinfected women to men makes this figure two to three times higher in discordant couples in which the susceptible partner is female.
To what extent can we extrapolate both the biologic and cost-effectiveness aspects of the data in this study to other settings? It is likely that the transmission effects we found are applicable to nonmonogamous heterosexual couples. Valacyclovir is effective in suppressing genital herpes in men who have sex with men.39 However, as shown in the trial, sexual transmission is influenced by sexual behavior and biologic factors. Most instances of HSV-2 transmission occur with source partners who do not have a history of genital herpes,5,15,38 and few studies describing daily antiviral medication in such persons are available. Additional studies to evaluate whether suppressive therapy will prevent transmission among couples with a source partner with subclinical HSV-2 infection, couples in whom the susceptible partner is immunocompromised, and homosexual couples should be undertaken. Studies in which the susceptible partner is pregnant are of special importance because of the high risk of acquisition of HSV-1 or HSV-2 infection in this setting. The few cases of asymptomatic HSV-1 acquisition in this study were not sufficient to allow us to determine whether valacyclovir would reduce the risk of HSV-1 transmission.
Because the observed reduction in the rate of transmission of genital herpes with valacyclovir is clinically relevant but not complete, it is important that disclosure of genital herpes to the susceptible partner and the practice of safer sex continue, since both may reduce the risk of transmission of genital herpes.
Supported by GlaxoSmithKline Research and Development and a grant (AI-30731) from the National Institutes of Health.
Dr. Corey reports supervision of laboratories that perform work on a contract basis for GlaxoSmithKline, Novartis, and 3M. Dr. Wald reports having received consultation fees from Biovail, Eli Lilly, and Novartis and lecture fees from GlaxoSmithKline. Dr. Patel reports having received consultation and lecture fees from GlaxoSmithKline and Novartis, consultation fees from Eli Lilly and 3M, and grant support from GlaxoSmithKline and reports holding equity in GlaxoSmithKline. Dr. Sacks reports having received consultation and lecture fees from GlaxoSmithKline and Novartis and holding equity in Viridae Clinical Sciences. Dr. Tyring reports having received consultation and lecture fees and grant support from GlaxoSmithKline. Dr. Warren reports having received consultation and lecture fees from GlaxoSmithKline. Dr. Douglas reports having received lecture fees from GlaxoSmithKline. Dr. Paavonen reports having received speakers' honorariums from GlaxoSmithKline. Dr. Morrow reports having received consultation fees from Bio-Rad, Focus, GlaxoSmithKline, and Novartis; lecture fees from Quest Diagnostics and Quadrant Health; and grant support from Trinity Bio-Tech. Dr. Beutner reports having received consultation and lecture fees from GlaxoSmithKline, Eli Lilly, and 3M. Dr. Mertz reports having received consultation fees from GlaxoSmithKline and Eli Lilly, lecture fees from GlaxoSmithKline, and grant support from 3M.
This article is dedicated to the memory of Stephen L. Sacks, M.D., whose research on genital herpes contributed substantially to our findings.
We are indebted to the 1498 couples, the investigators, and the study staff for their tremendous contribution to this demanding trial; to Julia Harris and Judith Zeh, statisticians, for their contributions to the analyses and study design, respectively; to Stacy Selke for her role in management of the data; to Zane Brown and Dorothea Griffiths for their work on the End-Points Committee; and to Alison Webster, Robert Deeter, and Karen Coates, all of GlaxoSmithKline, for their assistance.
* Members of the Valacyclovir Herpes Simplex Virus (HSV) Transmission Study Group are listed in the Appendix.
Source Information
From the Departments of Medicine (L.C., A.W.), Laboratory Medicine (L.C., R.A.M.), and Epidemiology (A.W.), University of Washington, Seattle; the Program in Infectious Diseases, Fred Hutchinson Cancer Research Center, Seattle (L.C.); the Department of Genitourinary Medicine, Royal South Hants Hospital, Southampton, United Kingdom (R.P.); Viridae Clinical Sciences and University of British Columbia, Vancouver, Canada (S.L.S.); the University of Texas Medical Branch, Galveston (S.K.T.); Westover Heights Clinic, Portland, Oreg. (T.W.); the Disease Control Service, Denver Department of Public Health, Denver (J.M.D.); the Department of Obstetrics and Gynecology, University of Helsinki, Helsinki, Finland (J.P.); Dow Pharmaceutical Sciences and Department of Dermatology, University of California, San Francisco (K.R.B.); the Department of Clinical Pharmacology, Smolensk State Medical Academy, Smolensk, Russia (L.S.S.); the Department of Medicine, University of New Mexico, Albuquerque (G.M.); and the Departments of Biomedical Data Sciences (O.N.K.) and Antiviral Clinical Research (H.A.W., D.T., M.V.-C.), GlaxoSmithKline Research and Development, Greenford, United Kingdom.
Address reprint requests to Dr. Corey at the Program in Infectious Diseases, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. N., Rm. D3-100, P.O. Box 19024, Seattle, WA 98109, or at lcorey@u.washington.edu.
References
Corey L, Wald A. Genital herpes. In: Holmes KK, M?rdh P-A, Sparling PF, et al., ed. Sexually transmitted diseases. 3rd ed. New York: McGraw-Hill, 1999:285-312.
Ashley R, Wald A. Genital herpes: review of the epidemic and potential uses of type-specific serology. Clin Microbiol Rev 1999;12:1-8.
Benedetti J, Corey L, Ashley R. Recurrence rates of genital herpes after symptomatic first-episode infection. Ann Intern Med 1994;121:847-854.
Wald A, Zeh J, Selke S, Ashley RL, Corey L. Virologic characteristics of subclinical and symptomatic genital herpes infections. N Engl J Med 1995;333:770-775.
Langenberg AGM, Corey L, Ashley RL, Leong WP, Straus SE. A prospective study of new infections with herpes simplex virus type 1 and type 2. N Engl J Med 1999;341:1432-1438.
Rooney JF, Felser JM, Ostrove JM, Straus SE. Acquisition of genital herpes from an asymptomatic sexual partner. N Engl J Med 1986;314:1561-1564.
Mertz GJ, Coombs RW, Ashley RL, et al. Transmission of genital herpes in couples with one symptomatic and one asymptomatic partner: a prospective study. J Infect Dis 1988;157:1169-1177.
Mertz GJ, Schmidt O, Jourden JL, et al. Frequency of acquisition of first-episode genital infection with herpes simplex virus from symptomatic and asymptomatic source contacts. Sex Transm Dis 1985;12:33-39.
Fleming DT, McQuillan GM, Johnson RE, et al. Herpes simplex virus type 2 in the United States, 1976 to 1994. N Engl J Med 1997;337:1105-1111.
Armstrong G, Schillinger J, Markowitz L, et al. Incidence of herpes simplex virus type 2 infection in the United States. Am J Epidemiol 2001;153:912-920.
Beyrer C, Jitwatcharanan K, Natpratan C, et al. Molecular methods for the diagnosis of genital ulcer disease in a sexually transmitted disease clinic population in northern Thailand: predominance of herpes simplex virus infection. J Infect Dis 1998;178:243-246.
Chen CY, Ballard RC, Beck-Sague CM, et al. Human immunodeficiency virus infection and genital ulcer disease in South Africa: the herpetic connection. Sex Transm Dis 2000;27:21-29.
Mwansasu A, Mwakagile D, Haarr L, Langeland N. Detection of HSV-2 in genital ulcers from STD patients in Dar es Salaam, Tanzania. J Clin Virol 2002;24:183-192.
Wald A, Link K. Risk of human immunodeficiency virus infection in herpes simplex virus type-2 seropositive persons: a meta-analysis. J Infect Dis 2002;185:45-52.
Corey L, Langenberg AGM, Ashley R, et al. Recombinant glycoprotein vaccine for the prevention of genital HSV-2 infection: two randomized, controlled trials. JAMA 1999;282:331-340.
Stanberry LR, Spruance SL, Cunningham AL, et al. Glycoprotein-D-adjuvant vaccine to prevent genital herpes. N Engl J Med 2002;347:1652-1661.
Carney O, Ross E, Bunker C, Ikkos G, Mindel A. A prospective study of the psychological impact on patients with a first episode of genital herpes. Genitourin Med 1994;70:40-45.
Douglas JM, Critchlow C, Benedetti J, et al. A double-blind study of oral acyclovir for suppression of recurrences of genital herpes simplex virus infection. N Engl J Med 1984;310:1551-1556.
Goldberg LH, Kaufman R, Kurtz TO, et al. Long-term suppression of recurrent genital herpes with acyclovir: a 5-year benchmark. Arch Dermatol 1993;129:582-587.
Wald A, Corey L, Cone R, Hobson A, Davis G, Zeh J. Frequent genital herpes simplex virus 2 shedding in immunocompetent women: effect of acyclovir treatment. J Clin Invest 1997;99:1092-1097.
Wald A, Warrant T, Hu H, et al. Suppression of subclinical shedding of herpes simplex virus type 2 in the genital tract with valaciclovir. In: Program and abstracts of the 38th Interscience Conference on Antimicrobial Agents and Chemotherapy, San Diego, Calif., September 24¨C27, 1998. Washington, D.C.: American Society for Microbiology, 1998:338. abstract.
Sacks SL, Hughes A, Rennie B, Boon R. Famciclovir for suppression of asymptomatic and symptomatic recurrent genital herpes shedding: a randomized double-blind, double-dummy, parallel-group, placebo-controlled trial. In: Program and abstracts of the 37th Interscience Conference on Antimicrobial Agents and Chemotherapy, Toronto, September 28¨COctober 1, 1997. Washington, D.C.: American Society for Microbiology, 1997:227. abstract.
Patel R, Bodsworth NJ, Woolley P, et al. Valaciclovir for the suppression of recurrent genital HSV infection: a placebo controlled study of once daily therapy. Genitourin Med 1997;73:105-109.
Genital herpes: a patient guide to treatment. Chicago: American Medical Association, 1997.
Spruance SL, Tyring SK, DeGregorio B, Miller C, Beutner K. A large-scale, placebo-controlled, dose-ranging trial of peroral valaciclovir for episodic treatment of recurrent herpes genitalis. Arch Intern Med 1996;156:1729-1735.
Wald A, Zeh J, Selke S, et al. Reactivation of genital herpes simplex virus type 2 infection in asymptomatic seropositive persons. N Engl J Med 2000;342:844-850.
Ryncarz AJ, Goddard J, Wald A, Huang ML, Roizman B, Corey L. Development of a high-throughput quantitative assay for detecting herpes simplex virus DNA in clinical samples. J Clin Microbiol 1999;37:1941-1947.
Jerome KR, Huang ML, Wald A, Selke S, Corey L. Quantitative stability of DNA after extended storage of clinical specimens as determined by real-time PCR. J Clin Microbiol 2002;40:2609-2611.
Fife KH, Barbarash RA, Rudolph T, Degregorio B, Roth R. Valaciclovir versus acyclovir in the treatment of first-episode genital herpes infection: results of an international, multicenter, double-blind, randomized clinical trial. Sex Transm Dis 1997;24:481-486.
Bacon TH, Levin JM, Leary J, Sarisky RT, Sutton D. Herpes simplex virus resistance to acyclovir and penciclovir after two decades of antiviral therapy. Clin Microbiol Rev 2003;16:114-128.
Gart JJ. Point and interval estimation of the common odds ratio in the combination of 2x2 tables with fixed marginals. Biometrika 1970;57:471-475.
Shuster JJ. Fixing the number of events in large comparative trials with low event rates: a binomial approach. Control Clin Trials 1993;14:198-208.
Zelen M. The analysis of several 2x2 contingency tables. Biometrika 1971;58:129-137.
Stamm W, Handsfield HH, Rompalo AM, Ashley RL, Roberts PL, Corey L. The association between genital ulcer disease and acquisition of HIV infection in homosexual men. JAMA 1988;260:1429-1433.
Brown ZA, Wald A, Morrow RA, Selke S, Zeh J, Corey L. Effect of serologic status and cesarean delivery on transmission rates of herpes simplex virus from mother to infant. JAMA 2003;289:203-209.
Wald A, Langenberg AGM, Link K, et al. Effect of condoms on reducing the transmission of herpes simplex virus type 2 from men to women. JAMA 2001;285:3100-3106.
Gardella C, Ashley R, Berry S, et al. The risk of acquisition of herpes simplex virus during pregnancy: a prospective couples study. Presented at the Annual Research Meeting of the Infectious Diseases Society for Obstetrics and Gynecology, Quebec City, Canada, August 9¨C11, 2001. abstract.
Wald A, Selke S, Lowens S, et al. Sexual transmission of genital HSV: risk factors in a time-to-event analysis. In: Program and abstracts of STIs at the Millennium: Joint Meeting of the American Sexually Transmitted Diseases Association/Medical Society for the Study of Venereal Diseases, Baltimore, May 3¨C7, 2000. abstract.
Conant MA, Schacker TW, Murphy RL, Gold J, Crutchfield LT, Crooks RJ. Valaciclovir versus aciclovir for herpes simplex virus infection in HIV-infected individuals: two randomized trials. Int J STD AIDS 2002;13:12-21.(Lawrence Corey, M.D., Ann)