Risk of HIV Transmission Through Breastfeeding

To the Editor: Dr Miotti and colleagues1 found a significant decrease in the risk of human immunodeficiency virus (HIV) transmission to infants after 6 months of breastfeeding in Malawi. However, some limitations may have weakened their conclusions.Whereas the main inclusion criterion was a negative polymerase chain reaction (PCR) result for HIV at 6 weeks of life, more than 25% of the children had tested negatively earlier (lower quartile, 1.4 months). For the many cases estimated to have occurred before 3 months of life (Figure 2, in their article), the first negative PCR result was probably obtained very early, at a minimum of 0.7 months, and the first positive PCR result shortly after. Even by using dried blood spot,2 timing of acquisition of HIV infection cannot be ascertained for these children, who were nevertheless considered as cases of postnatal transmission in the analysis. The authors' assumption of underestimation of postnatal transmission during the first semester of life seems therefore unlikely.