Parenteral Vaccine-Induced Antibody Levels in Children with Heavy Antibiotic Exposure in Dhaka, Bangladesh

Infants in resource-limited areas frequently receive early-life antibiotic treatment for respiratory and diarrheal illness, but the influence of antibiotics on parenteral vaccine immunogenicity in these settings remains underexplored. Therefore, we conducted a retrospective cohort study within a randomized, controlled, oral rotavirus and poliovirus vaccine trial performed in Dhaka, Bangladesh. Among 582 evaluable infants at 53 weeks of age, plasma antibody concentrations against measles, pertussis, diphtheria, tetanus, and Haemophilus influenzae type b (Hib) were evaluated for associations with prior antibiotic exposure. Most antibiotic prescriptions were broad-spectrum, with a mean of 85.5 days of antibiotics in the first year. Most children demonstrated protective antibody levels against measles (96%), tetanus (88%), and Hib (91%) at 53 weeks of age; fewer maintained protective levels against pertussis antigens (25-42%) and diphtheria (28%). Antibiotic exposure through 14 weeks of age, before completion of the primary vaccination series, did not significantly affect antibody concentrations at 53 weeks of age against diphtheria, tetanus, pertussis, and Hib antigens. Antibiotic exposure through 14 weeks of age was positively associated with measles antibodies at 53 weeks of age (change in concentration per antibiotic course was 9.09%; 95% CI: 5.13 to 12.75; q-value = 0.0003), but despite this association, nearly all children had protective antibody levels, limiting clinical significance. Although antibody levels varied by antigen, infant antibiotic exposure did not appear to clinically impact parenteral vaccine-induced antibody concentrations in this population. These findings support the robustness of parenteral vaccine responses in resource-limited settings despite high antibiotic use.