Assessment of Measles Incidence and Vaccination Coverage in Santa Catarina From 2013 to 2022: A Time-Trend Study

Measles is a highly contagious viral exanthematic disease, particularly severe in children under 5 years. Transmission occurs via nasopharyngeal secretions or aerosols. Diagnosis is clinical, and the most effective prevention is vaccination with the MMR vaccine (tríplice viral). In Brazil, the vaccine was introduced into the National Immunization Program (PNI) in 1993, with two recommended doses. The country eliminated the virus in 2016 but lost its certification in 2018 due to low vaccination coverage and reintroduction of the virus. In 2024, it regained certification. Low vaccination coverage, combined with social factors and failures in SUS, contributed to outbreaks. This study relates vaccination coverage to measles incidence in Santa Catarina over the last 10 years, aiming to analyze these data and correlate them with temporal trends from 2013 to 2022. Mixed observational, descriptive, and time-trend study, using data from the Department of Informatics of SUS and the Department of Epidemiological Surveillance. Statistical analysis was performed using simple linear regression, with p<0.05. From 2013 to 2022, 413 measles cases were recorded in Santa Catarina. One case was recorded in 2013, 304 in 2019, and 108 in 2020. Santa Catarina had first-dose MMR coverage above the recommended 95% in 2013, 2014, 2015, 2016, 2019, and 2022. For the second dose, the target was not met in any year of the period. There was a downward trend in first-dose vaccination (β -2.111; p=0.005), with a mean rate of 96.89% and a 9.24% reduction when comparing the first and last years. A stable trend was observed for the second dose, with a mean rate of 82.79%. The study indicates a downward trend in first-dose coverage and stability in second-dose MMR coverage in Santa Catarina. Factors such as vaccine hesitancy, misinformation, limitations within SUS, and the COVID-19 pandemic influenced vaccination adherence. Thus, declining coverage reflects a multifactorial problem involving social, structural, and contextual aspects. Therefore, it is essential that surveillance and immunization actions meet Ministry of Health targets, and that information dissemination and public awareness about the importance of vaccination be reinforced, to prevent the resurgence of measles in Brazil.