Condom effectiveness in reducing heterosexual HIV transmission

Area of Science:

• Public Health
• Epidemiology
• Infectious Disease Prevention

Background:

• The protective effect of condoms against HIV and other STIs is not fully quantified.
• Cohort studies of HIV serodiscordant couples offer a model to estimate disease incidence following known exposure.
• Comparing incidence rates between consistent condom users (100%) and non-users (0%) allows for effectiveness estimation.

Purpose of the Study:

• To estimate the effectiveness of condoms in reducing heterosexual HIV transmission.

Main Methods:

• Systematic literature search of electronic databases (AIDSLINE, CINAHL, Embase, MEDLINE) and reference lists.
• Inclusion criteria: longitudinal studies of HIV serodiscordant heterosexual couples with serological HIV status determination and condom usage data for 'always' or 'never' users.
• Data extraction included sample size, seroconversions, person-years of exposure, transmission direction, and STD presence; HIV incidence was calculated for 'always' and 'never' user cohorts.

Main Results:

• Fourteen studies were included, analyzing 13 cohorts of 'always' users with an HIV incidence of 1.14 per 100 person-years.
• Ten cohorts of 'never' users showed heterogeneous incidence, with longer follow-up studies yielding an estimate of 5.75 per 100 person-years.
• Overall condom effectiveness was estimated at approximately 80% reduction in HIV seroconversion.

Conclusions:

• Consistent condom use is associated with an 80% reduction in HIV incidence.
• Effectiveness, not efficacy, was estimated due to lack of data on 'correctness' of condom use in the reviewed studies.
• The findings apply generally to male condoms, with effectiveness comparable to, though lower than, that for contraception.