Variability in Vaccine Response and Trajectory in Early Childhood and Association With Demographic Variables, Antibiotic Exposure, and Infection Proneness.

Background: We sought to explore the variability of antibody responses to multiple vaccines during early life in individual children, assess the trajectory of each child longitudinally, determine the associations of demographic variables and antibiotic exposures with vaccine-induced immunity, and link vaccine responsiveness to infection proneness.

Methods: In 357 prospectively recruited children, aged 6-36 months, antibody levels to 13 routine vaccine antigens were measured in sera at multiple time points and normalized to their respective protective thresholds to categorize children into 4 groups: very low, low, normal, and high vaccine responders. Demographic variables and frequency of antibiotic exposure data were collected. Participants were followed to determine change in vaccine groups over time and occurrences of infections.

Results: Vaccine-induced antibody levels persisted over time as very low, low, normal, or high in individual children and changed post-primary through post-booster immunizations against multiple antigen types, including toxoids, purified proteins, polysaccharide-protein conjugates, recombinant proteins, and inactivated viruses. Factors influencing persistence or change in vaccine response group were assessed. Children who did not attend daycare and African American/multiracial children had higher vaccine-induced antibody levels than White children. Children with lower vaccine-induced antibody levels had more frequent antibiotic exposures. Low vaccine responsiveness was linked to more frequent antibiotic-treated bacterial infections.

Conclusions: When vaccine-induced antibody levels are used to define vaccine response groups, individual children may persist or change groups over time, which is associated with demographic variables and influenced by antibiotic exposures. Lower vaccine responsiveness can be linked to more frequent antibiotic-treated bacterial infections.