1. Influenza epidemiology and vaccine effectiveness during the 2023/2024 season in Italy: A test-negative case-control study
- Author
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Alexander Domnich, Giancarlo Icardi, Donatella Panatto, Marianna Scarpaleggia, Carlo-Simone Trombetta, Matilde Ogliastro, Federica Stefanelli, Bianca Bruzzone, and Andrea Orsi
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Influenza ,Influenza vaccine ,High-dose influenza vaccine ,Adjuvanted influenza vaccine ,Vaccine effectiveness ,Adults ,Infectious and parasitic diseases ,RC109-216 - Abstract
ABSTRACT: Objectives: In order to support policymakers in allocating resources, we aimed to assess vaccine effectiveness (VE) of inactivated influenza vaccines (IIVs) available for Italian adults in the 2023/2024 season. Methods: A hospital-based test-negative case-control study was conducted in Genoa between mid-October 2023 and mid-April 2024. Adult (≥18 years) inpatients with prescription of a polymerase chain reaction test for influenza were eligible. Results: Of 1,664 adults analyzed, most (82%) of which were ≥65 years, 114 (6.9%) tested positive for influenza A. Most (92%) cases were caused by subclades 6B.1A.5a.2a and 6B.1A.5a.2a.1 of the A(H1N1)pdm09 subtype. In older adults aged ≥65 years vaccination was effective at 51% (95% CI: 8%, 74%) against any influenza A and 49% (95% CI: 2%, 73%) against A(H1N1)pdm09. Compared with non-vaccinated older adults, VE point estimates for the adjuvanted and, especially, high-dose IIVs were higher than those for the standard-dose non-adjuvanted IIV. Conclusion: The 2023/2024 seasonal influenza vaccination proved moderately effective in preventing hospitalization for laboratory-confirmed influenza. Being more appropriate for older adults, local policymakers and vaccinating physicians should maximize adoption of the enhanced IIVs.
- Published
- 2024
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