A 25-year-old man reports having multiple female sexual partners. He asks how effective condoms are in preventing human immunodeficiency virus (HIV) infection.
How effective are male condoms in reducing heterosexual HIV transmission?
Evidence indicates that male condoms reduce the risk of heterosexual HIV transmission by 80 percent.
Programs for the prevention of HIV infection promote and measure condom use as an important element of HIV risk-reduction behavior.2–4 Some experts suggest that condoms may reduce HIV infection risk by as much as 90 percent,2 and the Centers for Disease Control and Prevention states that “latex condoms, when used consistently and correctly, are highly effective in preventing the sexual transmission of HIV….”5 Because a randomized trial to document the actual effectiveness of condoms for HIV infection prevention would be unethical, this review provides the best information available on the extent to which male condoms prevent transmission of HIV.
Background. The amount of protection that condoms provide against transmission of HIV and other sexually transmitted infections is unknown. Cohort studies of sexually active, HIV-serodiscordant couples with follow-up of the seronegative partner provide a situation in which a seronegative partner has known exposure to the disease, and disease incidence can be estimated. When some persons use condoms 100 percent of the time and some never use condoms, condom effectiveness can be estimated by comparing the infection incidence rates. Condom effectiveness is the proportionate reduction in disease as a result of condom use.
Objectives. The objective of this review is to estimate condom effectiveness in reducing heterosexual transmission of HIV.
Search Strategy. The authors1 used electronic databases (AIDSLINE, CINAHL, Embase, and MEDLINE) to identify relevant studies, and reference lists were searched by hand.
Selection Criteria. For inclusion, studies had to have data about sexually active, HIV-serodiscordant, heterosexual couples; a longitudinal study design; HIV status determined by serology; and contain condom usage information for a cohort of “always” (100 percent) or “never” (zero percent) condom users.
Data Collection and Analysis. Studies that met the inclusion criteria were reviewed for inclusion in the analysis. Sample sizes, number of seroconversions, and person-years of disease-free exposure time were recorded for each cohort. If available, the direction of transmission in the cohort (i.e., male-to-female, female-to-male), date of study enrollment, source of infection in the index case, and presence of other sexually transmitted diseases were recorded. Duplicate reports on the same cohort and studies with incomplete or nonspecific information were excluded. HIV incidence was estimated from the cohorts of always users and never users. Effectiveness was estimated from these two incidence estimates.
Primary Results. Of the 4,709 references that initially were identified, 14 were included in the final analysis. Thirteen cohorts of always users yielded a homogeneous HIV infection incidence estimate of 1.14 (95 percent confidence interval [CI], 0.56 to 2.04) per 100 person-years. Ten cohorts of never users appeared to be heterogeneous. The studies with the longest follow-up (mainly studies of partners of hemophiliac and transfusion patients) yielded an HIV incidence estimate of 5.75 (95 percent CI, 3.16 to 9.66) per 100 person-years. Overall effectiveness (i.e., the proportionate reduction in HIV seroconversion with condom use) is approximately 80 percent.
Reviewers' Conclusions. This review indicates that consistent use of condoms results in an 80 percent reduction in HIV infection incidence. Consistent use is defined as using a condom for all acts of penetrative vaginal intercourse. Because the studies used in this review did not report on whether condoms were used correctly for every act of intercourse, effectiveness and not efficacy is estimated. This estimate refers to the male condom in general, not specifically to the latex condom, because studies tended not to specify the type of condom that was used. Thus, condom effectiveness in reducing HIV transmission is similar to, although lower than, that for contraception.
These summaries have been derived from Cochrane reviews published in the Cochrane Database of Systematic Reviews in the Cochrane Library. Their content has, as far as possible, been checked with the authors of the original reviews, but the summaries should not be regarded as an official product of the Cochrane Collaboration; minor editing changes have been made to the text (http://www.cochrane.org).
The review reports HIV transmission rates per 100 person-years; these results suggest that of 100 heterosexually active, HIV-serodiscordant couples who do not use condoms, there would be five to seven new cases of HIV each year, and that if those same couples always used condoms, there would be only one new case each year. Therefore, condom use appears to provide 78 to 83 percent relative reduction in the risk of heterosexual HIV transmission.
Because these data come from multiple studies and different populations, they must be interpreted with caution. The “never users” appear to have more baseline HIV infection risk factors than the “always users” and may be at higher risk for having multiple partners. Comparing them with a lower risk group of “always users” may have given an artificially high estimate of risk reduction. Although the actual magnitude of HIV infection risk reduction from condom use for heterosexual intercourse likely will vary based on other risk factors and behaviors, the best evidence to date indicates that condom use reduces the risk of heterosexual HIV transmission by approximately 80 percent. Educating patients about this 80 percent risk reduction may help them understand more clearly how effective, even though imperfect, condoms are in protection against HIV transmission.