Introduction: Influenza is a seasonal acute respiratory infection with the potential to evolve into severe acute respiratory syndrome (SARS) and death. Its complications mainly affect children, the elderly, and individuals with comorbidities or immunosuppression. This study aimed to compare the incidence of influenza in Rio Grande do Sul (RS) between 2023 and 2025, analyzing hospitalizations, deaths, circulating subtypes, and vaccination coverage. A descriptive analysis using data from the Ministry of Health and the State Health Department of RS through SIVEP-Gripe (SARS) and Immunization panels, covering January 2023 to June 2025. Hospitalizations, deaths, seasonal distribution, viral subtypes, and vaccination coverage were evaluated. A progressive increase in influenza burden was observed in RS. In 2024, 2,328 hospitalizations and 288 deaths were recorded, representing increases of 45.7% and 46.8%, respectively, compared to 2023. Unvaccinated older adults accounted for 87.6% of hospitalizations and 87.2% of deaths, with a predominance of female and self-declared White patients. The H1N1 subtype predominated overall, while H3N2 was identified in 2024. A seasonal pattern was observed between epidemiological weeks (EW) 13 and 25. In 2023 and 2024, hospitalizations doubled during EW 13–17 and stabilized during EW 18–25. In 2025, hospitalizations decreased in EW 13–17 and then increased sharply in EW 18–25, nearly three times higher than in previous years. Deaths also increased, 2.6 times compared to 2023 and 2.4 times compared to 2024. Vaccination coverage remained below the 90% target: 56.4% in 2023, 52.3% in 2024, and 45.5% in 2025 (partial data through June). Between 2023 and 2025, influenza showed an increasing trend in RS, with significant impact on morbidity and mortality, especially among unvaccinated older adults. Low vaccination coverage remains a critical and persistent factor, requiring effective strategies to raise awareness and expand access to immunization. It reinforces the importance of achieving vaccination targets among priority groups and maintaining non-pharmacological measures, especially during seasonal periods of increased risk.
Oliveira et al. (Sun,) studied this question.