Adjuvanted vs High-Dose Influenza Vaccines in Older US Adults

Extracts from article abstract: 

"Objective: To assess the relative vaccine effectiveness (rVE) of adjuvanted vs high-dose inactivated influenza vaccine against polymerase chain reaction (PCR)–confirmed influenza in older adults at Kaiser Permanente Northern California (KPNC).

Results: This study included 429 595 individuals from the 2023 to 2024 influenza season (mean [SD] age, 75 [7] years; 236 857 [55.1%] female; 86 287 [20.1%] Asian, 22 910 [5.3%] Black, 53 820 [12.5%] Hispanic, 1123 [0.3%] American Indian or Alaska Native, 2562 [0.6%] Pacific Islander, 252 709 [58.8%] White, 1638 [0.4%] multiracial, and 8546 [2.0%] unknown race), of whom 212 875 (49.6%) received adjuvanted and 216 720 (50.4%) received high-dose influenza vaccine. There were 836 cases of PCR-confirmed influenza (3.9 per 1000 persons) identified after adjuvanted and 867 cases (4.0 per 1000 persons) after high-dose vaccine. The rVE of adjuvanted compared with high-dose influenza vaccine was 1.5% (95% CI, −8.4% to 10.5%) against influenza, 9.1% (95% CI, −4.0% to 20.4%) against influenza with hospitalization or emergency department visits, and 1.0% (95% CI, −11.4% to 12.0%) against hospitalizations for community-acquired pneumonia.

Conclusion and Relevance: In the first season of a large, ongoing study in adults 65 years or older, adjuvanted and high-dose influenza vaccines did not differ in effectiveness against laboratory-confirmed influenza during the 2023 to 2024 influenza season. Consistent with Advisory Committee on Immunization Practices recommendations, these results support the equivalency of adjuvanted and high-dose influenza vaccines for adults 65 years or older."

Hsiao, A., Leong, T., Fireman, B., Hansen, J., Zerbo, O., Jacobson, K.B., Liao, L.D., Haag, M.D.M., McGovern, I., Zhang, B., Dang, J. and Klein, N.P. (2026). Adjuvanted vs High-Dose Influenza Vaccines in Older US Adults. JAMA Network Open, 9(5), p.e2610120.