Impact of the COVID-19 pandemic on childhood immunization dynamics in Brazil, Paraná, and Maringá: an interrupted time series analysis (2018–2022)

Abstract

Objective: To analyze the impact of the COVID-19 pandemic on childhood immunization dynamics in Brazil, the state of Paraná, and the municipality of Maringá, focusing on changes in vaccination levels, temporal trends, and seasonal patterns of Pentavalent, Poliomyelitis, and Measles-Mumps-Rubella vaccines. Methods: This ecological, longitudinal, and retrospective study used monthly data from the National Immunization Program Information System (SI-PNI/DataSUS) from January 2018 to December 2022. Analyses included descriptive statistics, the Shapiro–Wilk normality test, comparison of medians between pre- and post-pandemic periods using the Mann–Whitney test, Spearman correlation to assess temporal trends and intergovernmental synchrony, and Interrupted Time Series (ITS) modeling with segmented linear regression. Model robustness was assessed using Newey–West heteroskedasticity- and autocorrelation-consistent standard errors. Results: A statistically significant reduction in medians and an acceleration of declining vaccination trends were observed in Brazil and Paraná after March 2020. In Maringá, no significant changes in level or trend were detected; however, increased variability and disruption of seasonal patterns were identified. Conclusion: The pandemic had a heterogeneous impact on childhood immunization, revealing sustained declines at national and state levels and operational instability at the municipal level.