In a first-of-its-kind study, researchers have found that antibiotic use in young children is associated with lower vaccine-induced antibody responses to several childhood vaccines.

The study, published yesterday in Pediatrics, found that children 2 years of age and younger who had received antibiotics had lower levels of antibody protection from the diphtheria-tetanus-acellular pertussis (DTaP) and pneumococcal conjugate vaccine (PCV) than those who received no antibiotics. They also found that antibiotic courses that were accumulated over time were negatively associated with vaccine-induced antibody levels.

While previous studies in mice and adult humans have suggested a link between antibiotics and the immune response to vaccination, the study is the first to find such a link in children. The study authors say the findings suggest an outcome that could leave children vulnerable to vaccine-preventable diseases and highlight the need for more research on antibiotics and vaccine-induced immunity.