Valacyclovir Prevents Sexual Transmission of HSV-2

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Summary and Comment

Valacyclovir Prevents Sexual Transmission of HSV-2

Once-daily treatment reduced transmission risk among heterosexual, HSV-2-discordant couples.

These researchers evaluated whether once-daily valacyclovir could reduce risk for transmission of herpes simplex virus-2 in an international, multicenter study funded jointly by the NIH and the drug manufacturer. Included in the analysis were 1484 heterosexual, monogamous couples who were discordant for HSV-2 infection. Infected partners (source partners) were randomized to receive oral valacyclovir (500 mg/day) or placebo for 8 months. Both partners were counseled about safer sex practices and were offered condoms at monthly clinic visits.

Participants (age, 18 or older; median, approximately 35) were immunocompetent and healthy and were using effective contraception. They had been in their current relationships for a median of 2 years. Of the source partners, 67% were female; the median duration of HSV-2 infection was 8 years in the valacyclovir group and 7 years in the placebo group. Approximately 90% of participants were white.

The partners of valacyclovir users were significantly less likely than those of placebo users to develop genital HSV-2 infection (1.9% vs. 3.6%) and symptomatic genital HSV-2 infection (0.5% vs. 2.2%). Overall, 37% of couples indicated that they never used condoms during the study, 20% reported condom use during more than 90% of sexual encounters, and 43% indicated less frequent use. Rates of HSV-2 transmission were lower in the valacyclovir group than in the placebo group for all levels of condom use.

Comment: More than 20% of U.S. adults have serologic evidence of HSV-2 infection. This study's findings indicate that chemoprophylaxis of sexual HSV-2 transmission now is a reality. Because condoms are partially effective in preventing HSV transmission, clinicians should continue to recommend their consistent use, as well as abstinence during outbreaks. Although this study does not address issues related to the optimal duration of valacyclovir use, it represents a major step forward in the prevention of genital HSV infection.

— Andrew M. Kaunitz, MD

Published in Journal Watch Women's Health February 24, 2004