Comparable Effectiveness of MF59®-Adjuvanted and High-Dose Quadrivalent Inactivated Influenza Vaccines for Prevention of Test-Confirmed Influenza During the 2022-2023 Influenza Season.

Objective: Adjuvanted and higher-dose influenza vaccines are recommended by the US Advisory Committee on Immunization Practices (ACIP) for adults ≥65 years. This study estimated the relative vaccine effectiveness (rVE) of adjuvanted quadrivalent influenza vaccine (aQIV) versus high-dose QIV (HD-QIV) in preventing test-confirmed influenza in US adults ≥65 years during the 2022-2023 season.

Methods: In a retrospective test-negative design, electronic health records and claims data from the Optum Market Clarity database were used to identify adults ≥65 years who received aQIV or HD-QIV and were tested for influenza associated with acute respiratory or febrile illness in any setting or during emergency department visits or inpatient admissions (ED/inpatient). A doubly robust model was used, combining inverse probability of treatment weighting and logistic regression.

Results: Of 4,228,481 adults ≥65 years who received aQIV or HD-QIV, 30,911 were tested for influenza and met selection criteria (2,361 cases; 28,550 controls). The rVE of aQIV vs. HD-QIV was -2.5% (95% CI, -13.4% to 7.4%) in any setting and 0.0% (95% CI, -15.9% to 13.7%) in ED/inpatient settings.

Conclusions: Similar to previous studies, aQIV and HD-QIV provided comparable protection against test-confirmed influenza in any setting, including ED/inpatient, aligning with ACIP and other recommendations for adults ≥65 years.