Background: Worldwide, mother-to-child transmission (MTCT) of human immunodeficiency virus type 1 (HIV) represents the most common means by which children acquire HIV infection. Efficacious and effective interventions to prevent in utero and intrapartum transmission of HIV infection have been developed and implemented. However, a large proportion of MTCT of HIV occurs postnatally, through breast milk transmission.
Objectives: The objectives of this systematic review were to collate and assess the evidence regarding interventions to decrease late postnatal MTCT of HIV, and to determine the efficacy of such interventions in decreasing late postnatal MTCT of HIV, increasing overall survival, and increasing HIV-free survival.
Search strategy: Electronic searches were undertaken using PubMed, EMBASE and other databases for 1980-2008. Hand searches of reference lists of pertinent reviews and studies, as well as abstracts from relevant conferences, were also conducted. Experts in the field were contacted to locate any other studies. The search strategy was iterative.
Selection criteria: Randomized clinical trials assessing the efficacy of interventions to prevent MTCT of HIV through breast milk were included in the analysis. Other trials and intervention cohort studies with relevant data also were included, but only when randomization was not feasible due to the nature of the intervention (i.e., infant feeding modality).
Data collection and analysis: Data regarding HIV infection status and vital status of infants born to HIV-infected women, according to intervention, were extracted from the reports of the studies.
Main results: Six randomized clinical trials and one intervention cohort study were included in this review. Two trials addressed the issue of shortening the duration of (or eliminating) exposure to breast milk. In a trial of breastfeeding versus formula feeding, formula feeding was efficacious in preventing MTCT of HIV (the cumulative probability of HIV infection at 24 months was 36.7% in the breastfeeding arm and 20.5% in the formula arm [p = 0.001]), but the mortality and malnutrition rates during the first two years of life were similar in the two groups. In a trial of early cessation of breastfeeding, HIV-free survival was similar between those children who ceased breastfeeding around four months of age and those who continued breastfeeding. Another trial addressing vitamin supplementation found more cases of HIV infection among children of mothers in the vitamin A arm. Efficacy for other vitamin supplements was not shown. An intervention cohort study evaluated the risk of MTCT according to infant feeding modality, and found increased risks of MTCT among breastfed children who also received solids (hazard ratio = 10.87, p = 0.018) as well as higher 3-month mortality rates (hazard ratio = 2.06) among infants given non- breast milk feedings (instead of exclusive breastfeeding). Three trials evaluated antiretroviral prophylaxis to breastfeeding infants. One trial found that breastfeeding with zidovudine prophylaxis (transmission rate = 9.0%) was not as effective as formula feeding (transmission rate 5.6%) in preventing late postnatal HIV transmission (p = 0.04). Breastfeeding with zidovudine prophylaxis and formula feeding had comparable HIV-free survival rates at 18 months (p = 0.60). Two trials of extended nevirapine prophylaxis demonstrated efficacy. In the first (data combined from trials conducted in three different countries), a six-week course of nevirapine resulted in a lower risk of HIV transmission by six weeks of age (p=0.009), but not at six months of age (p = 0.016). In the second, nevirapine administration until 14 weeks of age (5.2%) or nevirapine with zidovudine until 14 weeks of age (6.4%) resulted in significantly lower risks of MTCT of HIV by 9 months of age than a control regimen of peripartum prophylaxis (10.6%) (p < 0.001). HIV-free survival was significantly better through the age of 9 months in both extended prophylaxis groups, and through the age of 15 months in the extended nevirapine group.
Authors' conclusions: Complete avoidance of breastfeeding is efficacious in preventing MTCT of HIV, but this intervention has significant associated morbidity (e.g., diarrheal morbidity if formula is prepared without clean water). If breastfeeding is initiated, two interventions 1). exclusive breastfeeding during the first few months of life; and 2) chronic antiretroviral prophylaxis to the infant (nevirapine alone, or nevirapine with zidovudine) are efficacious in preventing transmission.