Pertussis, caused by the bacterium Bordetella pertussis, is an acute infectious disease with high transmissibility and an important cause of infant morbidity and mortality. Although pertussis can occur in different age groups, unvaccinated infants under 6 months of age born to unvaccinated mothers during pregnancy are the most vulnerable, due to the absence of specific immunity and the higher risk of severe forms of the disease. The main measure of protection against pertussis is vaccination of pregnant women with the Tdap vaccine and vaccination of infants with the pentavalent vaccine. Despite being available in the Brazilian Unified Health System (SUS), vaccine coverage has been declining in Brazil in recent years. To perform an epidemiological analysis of pertussis cases in children under 1 year of age in the state of São Paulo (SP), reported between 2015 and 2025, and relate them to vaccine coverage of the pentavalent and Tdap vaccines. This is a descriptive study with an epidemiological approach. Data were obtained from the DATASUS database (Department of Informatics of the Unified Health System). The variables analyzed were: year of notification, age group, sex, race/skin color, clinical outcomes, and vaccine coverage of pentavalent and Tdap vaccines. Between 2015 and 2025, 1,514 pertussis cases were reported in SP in children aged 1 to 11 months. Between 2018 and 2024, there was a 36.32% increase in cases. Children of both sexes were equally affected. In terms of clinical evolution, 89.08% were cured and 0.26% died. However, the highest proportion of deaths directly attributed to pertussis occurred in the first months of life, especially between 0 and 4 months of age, highlighting the greater vulnerability of this age group. Regarding vaccine coverage for pentavalent and Tdap vaccines, in 2015 the state reached 98.36% coverage for pentavalent and 61% for Tdap. By 2021, there was a decline in coverage for both pentavalent (67%) and Tdap (30%). The increase in pertussis cases in children under 1 year of age is strongly associated with the decline in vaccine coverage in recent years, especially after the COVID-19 pandemic. This scenario demands health policies that intensify vaccination campaigns, strengthen primary care teams, and combat misinformation.
Júnior et al. (Sun,) studied this question.