Reconstruction of malaria merozoites (green/purple) invading human red blood cells (red). Merozoites are covered in a fuzzy coating of surface proteins (light blue) that are shed during invasion. Image credit: NIAID (CC0 via unsplash)
Malaria alters the immune system during infection, but it remains unclear whether it leaves lasting effects. Previous studies have suggested that children living in malaria-endemic areas sometimes develop weaker responses to vaccines and other infections, indicating that early childhood exposure may influence immune responses many years later.
To explore the effect of malaria infection during early childhood, Safari et al. studied 123 children from two neighbouring communities on the Kenyan coast with different malaria histories. Over 15 years, children in both locations were closely followed with weekly visits to identify malaria cases; blood samples were collected annually.
Based on these data, Safari et al. reconstructed individual malaria exposure histories over time and measured antibody levels to different infections and vaccines over more than a decade. They analysed more than 1,200 serum samples and measured antibodies against a range of pathogens and vaccine antigens.
In one community, infection rates fell to negligible levels in 2004, while the other community experienced consistent malaria cases over the 15 years. Children who grew up in the area with a persistent malaria burden had lower antibody levels against several unrelated pathogens and vaccine antigens than children from the area where malaria had disappeared. These differences persisted throughout childhood. Safari et al. also found that children who experienced malaria early in life in the malaria-low community had lower antibody levels at 10 years of age than children in the same community who had never had malaria. The more malaria episodes a child experienced, the lower their antibody responses tended to be.
The findings of Safari et al. suggest that malaria may leave a long-lasting imprint on the immune system. If confirmed in other settings, this could help explain why vaccines are sometimes less effective in malaria-endemic regions and why the benefits of malaria control may extend beyond preventing malaria itself. Understanding how malaria influences long-term immune development could help improve vaccination strategies and child health in areas where malaria remains common.
