Influenza disease burden and the need for highly immunogenic vaccines in older adults: a narrative review.

Influenza presents a considerable disease burden, particularly among adults over 65 years old. In this population, the disease is associated with high rates of infection, hospitalization, and mortality. The objective of this study was to assess the impact of influenza on older adults and to evaluate the effectiveness of influenza vaccines within this demographic. A literature search was conducted using PubMed to identify relevant English-language studies published from January 2000 to January 2024. The analysis indicated that influenza-related hospitalization rates (ranging from 10.1 to 308.3 per 100,000 persons) and all-cause excess mortality rates (1.1 to 228.2 per 100,000 persons) were notably high in older adults, although these rates varied over time and by location. Hospitalization rates due to influenza increased considerably after the age of 50 years, with the highest rates observed in individuals aged 85 years and older. Excess mortality attributable to influenza also rose with age, with rates between 17.9 and 223.5 per 100,000 persons in those over 75 years old. The effectiveness of influenza vaccines in preventing severe infections requiring hospitalization was found to be only 37% in individuals aged 65 years and older. The unadjuvanted, standard-dose influenza vaccine had an estimated effectiveness of just 25% against laboratory-confirmed influenza and between 37% and 43.7% in preventing hospitalizations. Therefore, considering the substantial burden of influenza and the limited efficacy of standard vaccines, the use of highly immunogenic influenza vaccines should be prioritized for older adults.