An Ounce of Prevention

Sexually transmitted diseases (STDs), including HIV infections, are a global health priority. There are more than 20 sexually transmitted bacterial and viral infections. Each causes substantial long- and short-term morbidity and, in the case of HIV, mortality for infected persons, for their sexual partners, and for children born to infected mothers (1). Sexually transmitted diseases are a causal factor in the pathogenesis of squamous-cell carcinoma of the genital tract, a leading preventable cause of tubal factor infertility and ectopic pregnancy; are associated with adverse outcomes of pregnancy; and amplify risk for acquisition and transmission of HIV. Efforts to control STDs are best served by using a combined strategy aimed at identification and care for individuals with infection, and preventive measures for those at risk for infection. For many years, condoms have played a central role in efforts to prevent transmission or acquisition of STDs. However, during the past decade, people have challenged the utility of condoms for prevention of these diseases, mostly on the basis of ill-founded concerns that condom promotion might paradoxically encourage risky behaviors and because of the dearth of scientific proof that condoms are effective for prevention of STDs. To address the latter contention, the National Institutes of Health (NIH) convened an expert panel in June 2000 to critically review the published scientific evidence that condoms are effective for prevention of STDs. The panel's report (2) concluded that we have good evidence that condoms are effective for preventing HIV infection in women and men, and for preventing gonorrhea in men. However, we did not have rigorous, published evidence that condoms prevent other STDs. The panel also found that studies that considered condom effectiveness in their analyses of prevention of STDs tended to have methodologic shortcomings and low power. As a result, surprisingly few studies had adequately evaluated the effectiveness of condoms for preventing most common bacterial and viral STDs. Some took this conclusion to mean that condom promotion had no place in comprehensive risk reduction strategies. They argued that we should downplay condom promotion in favor of abstinence-only approaches in the prevention of STDs. The report and this interpretation of its conclusions served as a call to action for many investigators, leading to methodologic advances in study designs and to several careful studies that evaluated condom use for STD prevention (3-6). Why has good evidence of condom effectiveness for STD prevention been so hard to come by? Several reasons stand out (3). First, condom efficacy has rarely been the primary focus of studies. Second, many persons used condoms for some but not all sexual exposures, and many persons used condoms incorrectly or had them fail during use. Third, the measurement of condom use depends on self-report, so recall bias is a potential problem. Finally, the outcomes of interest (STDs) occur relatively infrequently even in at-risk persons and do not occur with every exposure to an infected partner. Because of these factors, study designs were complex and target enrollment was very high. Finally, because men transmit these diseases to women more efficiently than women transmit them to men, studies of condom effectiveness needed to measure infection rates separately for men and women. Much has been learned about condom effectiveness for prevention of STDs since the NIH condom workshop. In addition to already available evidence that latex condoms protect against acquisition of HIV in men and women and protect against gonorrhea in men, we now appreciate the limitations of condoms for prevention of STDs and have additional evidence of condom effectiveness. We know that many persons who use condoms do not use them properly or do not use them 100% of the time (4), reducing their protective effect; that condoms do sometimes break or slip off during use; and that there are some people prone to these forms of condom failure. We also have learned that, when properly used, condoms effectively reduce the likelihood of acquisition of Neisseria gonorrhoeae; Chlamydia trachomatis; and, for women, genital herpes (5-7). Likewise, we now more fully appreciate that although condoms reduce the risk for STDs, they do not offer 100% protection. In 2000, 1 of the most common STDs worldwide, genital herpes, was among the infections lacking sufficient evidence of condom effectiveness. Misunderstanding about the natural history of genital herpes infection and genital herpes transmission further complicated the evaluation of measures to prevent transmission. We used to think of genital herpes as a genital ulcer disease characterized by periodic painful clinical recurrences. We now appreciate that it is a chronic viral infection that has frequent asymptomatic recurrences and understand that viral shedding by asymptomatic persons who are unaware of their infection accounts for most genital herpes transmission (8). Only approximately 10% of the estimated 45 million Americans with genital herpes are aware of their infections (9). Consequently, long-term administration of valacyclovir reduces genital herpes transmission for persons in relationships in which 1 partner is known to have herpes (10). However, most persons with genital herpes are unaware of their infection and are therefore unlikely even to consider the potential benefits of long-term suppressive antiviral therapy. In this issue, Wald and coworkers (7) have further expanded the menu of proven measures for prevention of herpes transmission, showing that condoms protect men in a dose-dependent fashion with the degree of protection increasing in stepwise increments as condom use increases. Strengths of the study include its multicenter design; the large number of carefully evaluated participants; and use of serologic measures to detect infection, which allowed improved identification of persons who acquired infection during the course of the study. Taken in context, these data underscore the importance of promoting condoms as 1 element of comprehensive efforts to reduce STDs. Like other misperceptions about the importance of STDs and, in particular, genital herpes, people continue to harbor misperceptions about this infection's human costs. The impact of genital herpes is only partly related to the morbidity associated with the disease itself. Other consequences include transmission to sexual partners (most often by those who are unaware of their infections), transmission to newborns at the time of birth, and increased susceptibility to HIV acquisition. These consequences also lead logically to next steps in control of STDs. Proof that condoms help to reduce risk for acquisition of STDs provides clinicians with the weight of evidence behind their advice to use this tool for control of such diseases. Ongoing research and efforts to promote sexual abstinence, to reduce risk-taking behaviors, and to develop vaccines and topical microbicides for prevention of STDs should enhance efforts to control transmission and morbidity. For the present, however, condoms remain the best proven currently available means to reduce the risk for STDs in at-risk persons. Unfortunately, these individuals do not use condoms as much as they should. Clinicians should tell their at-risk patients that condoms can substantially reduce their risk for these diseases if they use them regularly. This simple message is our best weapon against STDs.