Specific IgG levels before and one month after administration of a booster dose of the diphtheria, tetanus, and pertussis vaccine in 14-year-old adolescents

BackgroundThe maintenance of durable humoral immunity against diphtheria, tetanus, and Bordetella pertussis during adolescence is critical for long-term protection and epidemiological stability. However, the immunological impact of booster vaccination at 14 years, particularly for pertussis, remains incompletely understood.MethodsIn this prospective, open-label study, 121 healthy 14-year-old adolescents received booster vaccination with Td-M (n = 34), Tdap (n = 51), or Tdap-M (n = 36).

Serum IgG antibodies against diphtheria and tetanus toxoids and B. pertussis were quantified by ELISA before and one month after vaccination.

Humoral responses were assessed using geometric mean titers and established seroprotection thresholds.ResultsAt baseline, all participants exhibited protective immunity to tetanus, while a minority lacked protective antibody levels against diphtheria (1.7%) and pertussis (6.9%). Booster vaccination elicited a robust increase in anti-diphtheria IgG across all groups, with no significant differences between vaccine formulations.

All adolescents achieved high levels of tetanus-specific antibodies, indicating strong anamnestic responses, with the highest titers observed in the Td-M group. In contrast, pertussis-specific IgG responses were heterogeneous and showed no overall increase following revaccination, suggesting limited booster-induced humoral expansion in previously primed individuals.