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The following is a summary of “Influenza epidemiology and vaccine effectiveness during the 2023/2024 season in Italy: A test-negative case-control study,” published in the October 2024 issue of Infectious Disease by Domnich et al.
Researchers conducted a retrospective study to assess the vaccine effectiveness of inactivated influenza vaccines available for Italian adults during the 2023/2024 season to inform resource allocation decisions for policymakers.
They examined adult inpatients (≥18 years) who were prescribed a polymerase chain reaction test for influenza in Genoa between mid-October 2023 and mid-April 2024.
The results showed that among 1,664 adults analyzed, the majority (82%) were aged ≥65 years, with 114 participants (6.9%) testing positive for influenza A. Most cases (92%) were attributed to subclades 6B.1A.5a.2a and 6B.1A.5a.2a.1 of the A(H1N1)pdm09 subtype. In older adults aged ≥65 years, vaccination demonstrated an effectiveness of 51% (95% CI: 8%, 74%) against any influenza A and 49% (95% CI: 2%, 73%) against A(H1N1)pdm09. Vaccine effectiveness (VE) point estimates for the adjuvanted and, notably, high-dose IIVs were higher than those for the standard-dose non-adjuvanted IIV compared to non-vaccinated older adults.
They concluded the 2023/2024 seasonal influenza vaccination demonstrated moderate effectiveness in preventing hospitalization due to laboratory-confirmed influenza.
Source: sciencedirect.com/science/article/pii/S120197122400273X
