Maternal HIV Infection and Antibody Responses in Uninfected Infants—Reply

In Reply: Ms de Souza and colleagues are concerned about factors that may have biased our results. While it has been documented that breastfeeding may affect responses to vaccination, it is unlikely to account for the differences we observed between HIV-exposed and unexposed infants. The majority of published data suggests that breastfeeding enhances rather than reduces vaccine responses,¹ specifically to diphtheria, tetanus, polio, BCG, and Haemophilus influenzae type b.^2- 3 Moon et al⁴ showed that higher levels of maternal IgA in breast milk can cause neutralization of live oral rotavirus antigens in vitro. We did not measure responses to rotavirus or any oral vaccine. We acknowledge that while breastfeeding may enhance the antibody response to some vaccines and potentially decrease the response to live oral vaccines, it would not explain our findings, namely increased responses among uninfected HIV-exposed infants to some vaccines, since all of these infants were exclusively formula fed. Therefore, we may in fact have underestimated the effect of HIV exposure on vaccine responses.