MMR Vaccination Coverage in 1-Year-Old Children in Brazil: Analysis of Adherence to the 1st and 2nd Doses and Risk of Measles Re-Emergence Based on the Anuário Vacinabr 2025

The MMR vaccine protects against measles, mumps and rubella—vaccine-preventable diseases with public health impact. Despite measles elimination in Brazil in 2016, declining vaccination coverage and abandonment of the 2nd dose have contributed to the emergence of outbreaks, undermining herd immunity. This study aims to analyze, based on 2023 data, adherence to the 1st and 2nd doses of MMR in 1-year-old children in Brazil, emphasizing regional differences and the risk of measles reintroduction. Descriptive study based on the Anuário VacinaBR 2025. Coverage of the 1st and 2nd MMR doses in 1-year-old children was analyzed in five states representing Brazil’s macro-regions: Tocantins, Maranhão, Mato Grosso do Sul, Rio de Janeiro and Rio Grande do Sul. Dropout rates were calculated by the difference between doses. The year 2023 was selected because it provides current and disaggregated data, enabling precise regional analyses. Results were compared with the 95% target defined by the Programa Nacional de Imunizações (PNI). In 2023, none of the states evaluated reached the target coverage for the complete schedule. Tocantins recorded 95.6% for the 1st dose and 47.9% for the 2nd, with a 47.7% dropout. Maranhão recorded 81.4% and 33.8%, respectively. In Rio de Janeiro, coverage was 70.1% and 36.9%. Mato Grosso do Sul showed the greatest decline (100.9% to 37.8%), with 63.1% dropout. Rio Grande do Sul, despite the best performance, remained below target: 94.2% for the 1st dose and 64.4% for the 2nd. There was good initial adherence followed by a marked drop in the 2nd dose, especially in the North, Northeast and Center-West regions. Low MMR coverage, combined with high dropout, exposes Brazil to the risk of measles reintroduction, especially in regions with structural vulnerabilities and reduced adherence. This scenario calls for measures such as strengthening epidemiological surveillance, addressing vaccine hesitancy and improving primary care. Regionalized analysis identifies priority territories and reinforces the need for coordinated interventions to restore herd immunity and avoid setbacks in public health.