Scientists have found that babies whose mothers have HIV, but are not HIV-infected themselves, are born with lower levels of specific proteins in their blood called antibodies, which fight infection, compared with babies not exposed to HIV. The finding, by scientists from Imperial College London and Stellenbosch University in South Africa, might explain in part why uninfected babies born to women with HIV have a higher risk of illness and death early in life. The new study found that babies born to HIV-infected mothers had significantly lower levels at birth of antibodies against a range of bacterial infections (Hib, pertussis, pneumococcus and tetanus). The study found lower levels of some specific antibodies in mothers with HIV, but also that less antibody is transferred from mother to child across the placenta. However, despite their low antibody levels at birth, the babies in the study responded well to vaccination: they produced similar levels of antibody to some vaccines and higher levels to other vaccines. The study involved 109 HIV-infected and uninfected mothers in a community health centre in Khayelitsha, a rapidly-growing township in Cape Town, South Africa. The findings have been published in the Journal of the American Medical Association.