Antibiotic prescriptions for children aged 6-24 months are associated with reduced vaccine-induced immunity, according to a study published in Pediatrics. Michael E. Pichichero, MD, and colleagues examined 560 children aged 6-24 months to assess the association between antibiotic use and vaccine-induced immunity. Children given antibiotics had lower vaccine-induced antibody levels to several diphtheria-tetanus-acellular pertussis (DTaP) and pneumococcal conjugate (PCV) antigens. At ages 9 and 12 months, a higher frequency of vaccine-induced antibodies below protective levels was seen in children given antibiotics. There was a negative association observed for antibiotic courses over time with vaccine-induced antibody levels. For each antibiotic course the child received, pre-booster antibody levels decreased by 5.8%, 6.8%, 11.3%, and 10.4% to DTaP, Haemophilus influenzae type b, inactivated polio, and PCV antigens, respectively, while post-booster antibody levels decreased by 18.1%, 21.3%, 18.9%, and 12.2%, respectively. “We provide new evidence to suggest caution about overprescribing antibiotics because an adverse effect seems to extend to reduction in vaccine responses,” the authors wrote.