Sero-Epidemiology of Pertussis in the Municipality of Duque de Caxias, Rio de Janeiro, Brazil: A Case Study

Background: Whooping cough (pertussis), caused by Bordetella pertussis, remains a major public health concern worldwide despite high vaccination coverage. Resurgent outbreaks underscore the need for continued epidemiological and immunological monitoring to evaluate population immunity. To assess the humoral immune protection in children aged 1–14 years vaccinated with DTP/Hib/HB between January and December 2022 in Duque de Caxias, Rio de Janeiro, Brazil. Methods: A total of 220 serum samples were analyzed using commercial ELISA kits to detect circulating IgG antibodies against pertussis toxin (PTx) and B. pertussis antigens. Antibody levels were compared across age groups using the Kruskal–Wallis test followed by Dunn’s multiple comparisons. Results: Anti-PTx antibody levels were low across all age groups, with only 2.17% of children showing seropositive levels (>40 IU/mL). Broader reactivity to B. pertussis antigens (PTx + FHA) was detected in 36.7% of samples, but antibody titers declined significantly with increasing age (p < 0.05). These findings indicate waning vaccine-induced immunity and potential susceptibility to reinfection. Conclusions: The study reveals low levels of circulating IgG antibodies against pertussis among vaccinated children, emphasizing the need to reassess the current immunization schedule. Introduction of adolescent booster doses and expanded access to acellular pertussis vaccines are recommended to enhance long-term protection.