Seroincidence of HIV-1 infection in African women of reproductive age: a prospective cohort study in Kigali, Rwanda, 1988-1992.

Objective: To estimate the seroincidence of HIV-1 infection among women of reproductive age in Kigali, Rwanda.

Design: Fixed prospective cohort followed for 36 months between November 1988 and June 1992, as part of an ongoing study of mother-to-child transmission of HIV-1.

Setting: Centre Hospitalier, Kigali, Rwanda.

Subjects: A total of 216 HIV-seronegative women were enrolled at delivery between November 1988 and June 1989.

Methods: A blood sample was obtained at delivery to test for HIV antibodies (by enzyme-linked immunosorbent assay and Western blot). Serum was tested every 3 months during follow-up. Incidence density rates of HIV seroconversion were estimated.

Results: The follow-up rate after 3 years was 89%, assessed by the maximum person-years method. The seroincidence density rate was 3.5 per 100 women-years (95% confidence interval, 1.9-5.0). It decreased linearly from 7.6 during the first 6-months postpartum to 2.5 per 100 women-years during the last 6 months of the third year of follow-up. Maternal age did not affect HIV incidence rates. We examined the role of the cohort, counselling, and the first 6-month postpartum effects on this estimate.

Conclusion: This fixed cohort provided an overall estimation of the HIV infection incidence rate and its dynamics. These figures could be used for programming future HIV preventive vaccine efficacy trials in Rwanda.