Enhanced influenza vaccines impact effectiveness in individuals aged 65 years and older, Denmark, 2024/25 influenza season up to 4 March 2025

During the 2024/25 influenza season, enhanced and standard-dose influenza vaccines were available for individuals aged 65 and older. Compared with the standard-dose quadrivalent influenza vaccine (QIV), the adjuvanted QIV was significantly more effective, with an overall vaccine effectiveness (VE) of 48% (95% CI: 42-52) vs 33% (95% CI: 24-41) when considering both non-hospitalised and hospitalised patients. The high-dose QIV demonstrated similar effectiveness to the adjuvanted QIV. These findings support the inclusion of enhanced influenza vaccines in future vaccination programmes.