Adherence to extended postpartum antiretrovirals is associated with decreased breast milk HIV-1 transmission

Objective: Estimate association between postpartum antiretroviral adherence and breast milk HIV-1 transmission. Design: Prospective cohort study. Methods: Mother-infant pairs were randomized after delivery to immediately begin receiving 28 weeks of either triple maternal antiretrovirals (zidovudine, lamivudine, and either nevirapine, nelfinavir, or lopinavir-ritonavir) or daily infant nevirapine as part of the Breastfeeding, Antiretrovirals, and Nutrition (BAN) study. Associations between postpartum antiretroviral adherence and rate of breast milk HIV-1 transmission were estimated using Cox models. We measured adherence over four postpartum time intervals using pill count, suspension bottle weight, and maternal self-report. Adherence was categorized and lagged by one interval. Missing adherence measures were multiply imputed. Infant HIV-1 infection was determined by DNA PCR every 2-6 weeks. The primary endpoint was infant HIV-1 infection by 38 weeks of age among infants alive and uninfected at 5 weeks. Results: Analyses included 1479 mother-infant pairs and 45 transmission events. Using pill count and bottle weight information, 22-40% of mother-infant pairs at any given interval were less than 90% adherent. Having at least 90% adherence was associated with a 52% [95% confidence interval (CI) 3-76] relative reduction in the rate of breast milk HIV-1 transmission, compared with having less than 90% adherence when controlling for study arm, breastfeeding status, and maternal characteristics. Complete case analysis rendered similar results (n = 501; relative reduction 59%, 95% CI 6-82). Conclusion: Nonadherence to extended postpartum antiretroviral regimens in 'real world' settings is likely to be higher than that seen in BAN. Identifying mothers with difficulty adhering to antiretrovirals, and developing effective adherence interventions, will help maximize benefits of antiretroviral provision throughout breastfeeding. (C) 2014 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins