Condom effectiveness in reducing heterosexual HIV transmission

Area of Science:

• Epidemiology
• Public Health
• Infectious Diseases

Background:

• The protective effect of condoms against HIV and other STDs remains incompletely understood.
• Cohort studies of HIV-serodiscordant couples offer a unique model for estimating disease incidence and condom effectiveness.
• Comparing incidence rates between consistent condom users (100%) and non-users (0%) allows for effectiveness estimation.

Purpose of the Study:

• To quantitatively assess the effectiveness of condoms in preventing heterosexual HIV transmission.
• To synthesize data from relevant cohort studies to provide a robust estimate of condom effectiveness.

Main Methods:

• Systematic literature search of electronic databases (AIDSLINE, CINAHL, Embase, MEDLINE) and reference lists.
• Inclusion criteria: HIV-serodiscordant heterosexual couples, longitudinal design, serological HIV status determination, and data on consistent (100%) or non-use (0%) of condoms.
• Data extraction included sample size, seroconversions, person-years of exposure, transmission direction, and STD presence; HIV incidence was calculated for both user groups.

Main Results:

• Fourteen studies with 13 cohorts of 'always' condom users showed a homogeneous HIV incidence of 1.14 per 100 person-years.
• Ten cohorts of 'never' condom users exhibited heterogeneity, with longer follow-up studies yielding an incidence of 5.75 per 100 person-years.
• Overall, consistent condom use demonstrated an approximate 80% reduction in HIV seroconversion.

Conclusions:

• Consistent condom use, defined as using a condom for all penetrative vaginal intercourse acts, reduces HIV incidence by approximately 80%.
• The study estimates condom 'effectiveness' (real-world use) rather than 'efficacy' (ideal use) due to lack of data on correctness of use.
• Findings generally apply to male condoms, with effectiveness comparable to, though lower than, contraceptive effectiveness.