Recombinant or Standard-Dose Influenza Vaccine in Adults under 65 Years of Age

This cluster-randomized observational study at Kaiser Permanente Northern California compared the effectiveness of high-dose recombinant influenza vaccine (Flublok Quadrivalent) versus standard-dose egg-based vaccines across the 2018–2019 and 2019–2020 seasons. Encompassing 1.63 million adults aged 18–64 years, the analysis focused primarily on the 50–64 age group. Among this cohort, PCR-confirmed influenza rates were 2.00 per 1000 vaccinees in the recombinant group and 2.34 per 1000 in the standard-dose group, yielding a relative vaccine effectiveness of 15.3% (P=0.002). Effectiveness against influenza A was similarly 15.7% (P=0.002). No statistically significant difference was found in influenza-related hospitalization rates between vaccine groups. The study concludes recombinant vaccines confer modestly greater protection against lab-confirmed influenza in adults under 65.

This cluster-randomized observational study at Kaiser Permanente Northern California compared the effectiveness of high-dose recombinant influenza vaccine (Flublok Quadrivalent) versus standard-dose egg-based vaccines across the 2018–2019 and 2019–2020 seasons. Encompassing 1.63 million adults aged 18–64 years, the analysis focused primarily on the 50–64 age group. Among this cohort, PCR-confirmed influenza rates were 2.00 per 1000 vaccinees in the recombinant group and 2.34 per 1000 in the standard-dose group, yielding a relative vaccine effectiveness of 15.3% (P=0.002). Effectiveness against influenza A was similarly 15.7% (P=0.002). No statistically significant difference was found in influenza-related hospitalization rates between vaccine groups. The study concludes recombinant vaccines confer modestly greater protection against lab-confirmed influenza in adults under 65.