• Robertus van Aalst, Stefan Gravenstein, Vincent Mor, Salaheddin M Mahmud, Jan Wilschut, Maarten Postma, and Ayman Chit.
• Department of Health Sciences, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands; Vaccine Epidemiology and Modelling, Sanofi Pasteur, Swiftwater, PA, USA. Electronic address: rob.vanaalst@sanofi.com.
• Vaccine. 2020 Jan 10; 38 (2): 372-379.

BackgroundAdults 65 years and older (seniors) experience more complications following influenza infection than younger adults. We estimated the relative vaccine effectiveness (rVE) of a trivalent high dose (HD-IIV3) versus an adjuvanted trivalent influenza vaccine (aIIV3) in seniors for respiratory-related hospitalizations.MethodsWe conducted a retrospective cohort study using claims data from Optum's Clinformatics® Data Mart to compare outcome rates between seniors who received HD-IIV3 versus aIIV3 during the 2016/17 and 2017/18, predominantly A/H3N2 respiratory seasons. Rates were adjusted for demographic characteristics, comorbid conditions, previous influenza vaccination, and geography. We used the previous event rate ratio (PERR) approach to address bias by time-fixed unmeasured confounders.ResultsWe identified 842,282 HD-IIV3 and 34,157 aIIV3 recipients for the 2016/17 season and 1,058,638 HD-IIV3 and 189,636 aIIV3 recipients for the 2017/18 season. The pooled rVE of HD-IIV3 versus aIIV3 for respiratory-related hospitalizations over both seasons was 12% (95% confidence interval: 3.3%-20%); 13% (-6.4% to 32%) for the 2016/17 season and 12% (2.1%-21%) for the 2017/18 season.ConclusionsPooled over two predominantly A/H3N2 respiratory seasons, HD-IIV3 was associated with fewer respiratory hospital admissions than aIIV3 in senior members of large national managed health care company in the U.S.Copyright © 2019 The Author(s). Published by Elsevier Ltd.. All rights reserved.

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