The results show that some children in the vaccinated group had antibodies that were highly reactive to a small subset of malaria antigens not contained in the vaccine. The levels of these ‘off-target’ antibodies correlated strongly with anti-CSP levels, declined similarly over time and increased again with a booster dose. “This strongly suggests that, in some children, the vaccine is inducing antibodies that can also recognise other malaria antigens,” says Dídac Macià, first author of the study.
Children who developed higher off-target antibodies were less likely to develop clinical disease. In other words, “strong responses to other malaria antigens were a predictor of increased vaccine protection, beyond what anti-CSP levels alone could predict,” says Dobaño. The researchers now need to confirm whether this off-target response confers greater protection against malaria, or whether it is only a marker of efficient vaccine responses.
Although imperfect, RTS,S may offer more than we bargained for.
Photo: ©WHO, Fanjan Combrink