Although condom use reduces the risk of sexually transmitted diseases (STDs) such as human immunodeficiency virus and gonorrhea, until recently the effectiveness of condoms in the prevention of genital herpes was unclear. Condoms are thought to offer incomplete protection from herpes simplex because the virus may infect external genitalia not covered by the condom. Herpes simplex virus type 2 (HSV-2) is the predominant cause of genital herpes; a small percentage of infections are caused by herpes simplex virus type 1 (HSV-1). Wald and colleagues studied the association between self-reported condom use and acquisition of HSV-1 and HSV-2 in a cohort of high-risk adults who participated in a trial for an HSV-2 vaccine that was later shown to be ineffective.

The study included 1,862 HSV-2 seronegative persons who were recruited from 22 clinics in the United States. Inclusion criteria were four or more sex partners or one or more STDs in the previous year. The average age was 27 years; 64 percent of participants were seropositive for HSV-1. Information about frequency of sexual activity, frequency of condom use, number of new partners, and number of partners with a known history of genital herpes was collected over the next 18 months. Nineteen participants reported no sexual activity during the study and were excluded from the final analysis. The remaining participants were divided into three groups based on self-reported frequency of condom use: 0 to 25 percent of the time (40 percent of patients); 25 to 75 percent of the time (31 percent); and more than 75 percent of the time (29 percent).

HSV-2 seroconversion occurred in 6.4 percent of participants during the study. An increased risk of seroconversion was associated with female sex (relative risk [RR] = 1.79); men who have sex with men (RR = 2.65); age younger than 27 years (RR = 1.62); more than two sexual activities per week (RR = 1.77); and having a partner with a history of genital herpes (RR = 2.30). After statistical adjustment for these factors, a stepwise association was observed between increasing frequency of condom use and decreasing rates of HSV-2 seroconversion. Although 8 percent of participants who reported never using condoms acquired HSV-2, only 4.6 percent of those who reported using condoms more than 75 percent of the time acquired the condition. There was no association between frequency of condom use and HSV-1 seroconversion.

The authors conclude that more frequent condom use was associated with a lower risk of acquiring HSV-2 regardless of frequency or type of sexual activity. Although condoms were not 100 percent effective in preventing infection, the authors caution that this study did not assess whether condoms were used correctly. They assert that encouraging consistent condom use remains a worthwhile strategy for preventing genital herpes in sexually active persons.

editor's note: Although herpes simplex virus 2 (HSV-2) often is perceived as a nuisance compared with other sexually transmitted diseases, it is now recognized for its significant societal consequences (e.g., lifelong morbidity, perinatal transmission, increased risk of human immunodeficiency virus).¹ As in any observational cohort study, Wald and colleagues' data only demonstrate an association, not a causal relationship. Because the effectiveness of condoms probably will never be tested in a randomized controlled trial, their role in genital herpes prevention likely will continue to be debated. Nonetheless, this new evidence is the strongest to date that the effectiveness of condoms increases with more frequent use. —k.w.l