Measles vaccination elicits a polyfunctional antibody response, which decays more rapidly in early vaccinated children.

Background Measles outbreaks are reported worldwide posing a serious threat, especially to young unvaccinated infants. Early measles vaccination under 12 months of age can induce protective antibody levels, but the long-term antibody functionalities are unknown. Methods Measles-specific antibody-functionality was tested by systems serology, in children receiving an early measles vaccination at 6-8 or 9-12 months, followed by a regular dose at 14 months of age, and children only receiving the vaccination at 14 months. Antibody-functionalities comprised complement-deposition, cellular cytotoxicity, neutrophil and cellular phagocytosis. Pearson's r correlations between all effector functions were used to investigate the coordination of the response. Results Children receiving early measles vaccination at 6-8 or 9-12 months show polyfunctional antibody responses. Despite significant lower levels of antibodies in these early-vaccinated children, Fc-effector functions were comparable with regular-timed vaccinees at 14 months. However, 3-year follow-up revealed significant decreased polyfunctionality in children that received a first vaccination at 6-8 months, but not in children that received the early vaccination at 9-12 months. Conclusions Antibodies elicited in early-vaccinated children are equally polyfunctional to those elicited from children who received vaccination at 14 months. However, these antibody-functionalities decays more rapidly than those induced later in life, which may lead to suboptimal long-term protection.