Vacinação Infantil no Brasil : cobertura de rotina e vacinas das Hepatites A e B

Abstract

In a scenario of sharp decline in infant vaccination coverage in Brazil, this thesis advances the frontier of knowledge by conducting an integrated analysis, investigating systemic failures and access barriers as central determinants of the crisis. Objective: To evaluate infant vaccination coverage in Brazil, with emphasis on hepatitis A and B vaccines, in order to understand the drop in immunization rates and their determinants. Methods: The thesis articulated three studies with a progressive logic. First, a systematic review (1980-2024) of 38 studies mapped the historical scenario and research gaps. Subsequently, two observational studies deepened the analysis using data from a national survey (ICV 2020-2022) with up to 37,801 children born in 2017 and 2018. The first study used a historical cohort design to analyze the timeliness of the hepatitis B birth dose, complete adherence to the vaccination schedule, and zero-dose status, using multivariate logistic regression models. The second adopted a cross-sectional design, with robust Poisson regression, to estimate prevalence ratios of non-vaccination against hepatitis A, stratifying by sociodemographic and contextual determinants. Results: The systematic review identified three phases of vaccine evolution in Brazil: continuous expansion until 2015, sharp decline (2016-2021), and partial recovery (from 2022), marked by deep regional inequalities (superior performance in the South/Southeast versus structural failures in the North/Northeast). The observational studies showed performance below national targets, with timely coverage of the hepatitis B birth dose at 58.5% and hepatitis A at 24 months at 88.1%. Vaccination failures are concentrated in groups exposed to social vulnerability, population mobility, and weaker ties with health services. Conclusion: The study concludes that the post-2016 vaccine decline constitutes a structural crisis of immunization, and not merely individual hesitancy. Failures are concentrated in groups exposed to social vulnerability and the fragility of ties with Primary Health Care (PHC). Reversal requires a State response focused on equity, prioritizing the strengthening of PHC, the improvement of information systems, and active search strategies for underserved populations. Final Considerations: The thesis offers an integrated understanding of the vaccine crisis, articulating the historical trajectory, regional inequalities, and contemporary social determinants. By highlighting the concentration of failures in invisible groups, the work reaffirms immunization as an imperative of health justice. The sustainability of the National Immunization Program requires strong governance, stable funding, and programmatic innovation to ensure equity and the fundamental right to health for all children.