Izurieta HS, Lu M, Kelman J, et al. - Researchers examined all influenza vaccines for their relative effectiveness among Medicare beneficiaries ages > 65 years to prevent influenza hospital encounters during the 2019-20 season. They used Poisson regression and inverse probability of treatment weighting (IPTW) to conduct this retrospective cohort study. Exposures included egg-based high-dose trivalent (HD-IIV3), egg-based adjuvanted trivalent (aIIV3), egg-based standard dose (SD) quadrivalent (IIV4), cell-based SD quadrivalent (cIIV4), and recombinant quadrivalent (RIV4) influenza vaccines. A total of 12.7 million vaccinated beneficiaries were studied. Findings revealed moderately high effectiveness of RIV4 than other vaccines in this influenza B-Victoria and A(H1N1)-dominated season, while higher effectiveness was reported for the HD-IIV3 and aIIV3 vs the IIV4 vaccines, suggesting the contributions of antigen amount and adjuvant use to VE. No substantial effect of the egg adaptation on RVE evaluation appeared.