Breast-feeding and HIV-1 transmission -- how risky for how long? [editorial]

Breast milk transmission of HIV-1 continues to present enormous challenges for prevention of infant HIV-1 infection. Breast milk confers a variety of benefits to infants but can also be a vehicle for HIV- 1 transmission. Determining the amount of risk due to breast-feeding duration of risk and cofactors for risk is useful for designing efficient interventions to decrease the incidence of infant HIV-1 infection. In this issue of the Journal Taha et al. evaluated late postnatal transmission in cohorts of Malawian mother-infant pairs who participated in 2 previously published clinical trials of antiretrovirals to prevent mother-to-child transmission (the nevirapine-zidovudine studies). Overall 1256 infants without HIV-1 infection at 1.5 months were monitored for 24 months to determine the risk of late postnatal transmission. The risk of HIV-1 acquisition in this group was 9.7% and the vast majority (87.4%) of late infections occurred after 6 months of age. The study was large yielded a fairly precise risk estimate and included a 2-year follow-up which enabled comparison of risk estimates for serial intervals of ~6 months. Interestingly the 1.5-6-month age interval was the one with the lowest risk of HIV-1 transmission (1.22%). Finally utilizing the cohorts size and long follow-up period the authors were also able to identify several significant correlates of late postnatal transmission. (excerpt)