Influenza Vaccination Appropriateness: Insights from the Local Health Unit of Catania During the 2023/2024 and 2024/2025 Seasons.

Background/Objectives: Influenza poses a substantial global public health challenge, disproportionately affecting vulnerable populations. Vaccination is the most effective preventive measure, and recent strategies in Italy emphasize the principle of "appropriateness"-the alignment of specific vaccine formulations (e.g., adjuvanted or high-dose) with targeted risk groups to optimize protection. Nevertheless, challenges persist in ensuring the consistent administration of the most suitable vaccine, particularly among high-risk individuals who would benefit most. Methods: A retrospective descriptive study was conducted using data from the 2023-2024 and 2024-2025 influenza vaccination campaigns of the Local Health Authority of Catania. Vaccination data were analyzed by age group and vaccine type, based on national immunization guidelines. Population categories included individuals ≥ 65 years, adults 60-64 years, adults 18-59 years (with/without chronic conditions), children, and pregnant/postpartum women. Vaccine types analyzed were aQIV, QIV-HD, QIV-SD, QIVcc, and LAIV. Descriptive statistics were used, and Relative Risk (RR) with 95% Confidence Intervals (CI) was calculated using the 60-64 age group as a reference. Analyses were performed with Stata 18.0. Results: In 2023-2024, 78.8% of individuals ≥ 65 received recommended vaccines, compared to 100% in the 60-64 group (RR = 0.23; 95% CI: 0.225-0.231). Adults 18-59, children, and pregnant/postpartum women showed ≥99% adherence. In 2024-2025, appropriateness in the ≥65 group improved to 96.1% (RR = 0.12; 95% CI: 0.118-0.128). All other groups maintained high adherence (≥99%), except for 6.2% of children aged 6 months-2 years who inappropriately received LAIV. Conclusions: Despite dramatically improved vaccination appropriateness in the elderly, a persistent and critical safety issue--inappropriate administration LAIV use in 6.2% of young children-highlights the need for targeted interventions to ensure complete patient safety.