Comparative effectiveness of high dose versus adjuvanted influenza vaccine: A retrospective cohort study

Robertus Van Aalst,Stefan Gravenstein,Vincent Mor,Salaheddin M Mahmud,Jan Wilschut,Maarten Postma,Ayman Chit

doi:10.1016/j.vaccine.2019.09.105

Abstract

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.

Highlights

Adults 65 years and older experience more complications following influenza infection than younger adults
Pooled over two predominantly A/H3N2 respiratory seasons, HD-IIV3 was associated with fewer respiratory- and cardiorespiratory-related hospital admissions than aIIV3 in senior members of large national managed care company in the U.S
For these two reasons, it is challenging to quantitatively compare the relative vaccine effectiveness (rVE) between our study and Izurieta et al; it is noteworthy that directionally HDIIV3 is in both studies associated with reduced hospitalization rates compared to aIIV3

Summary

Introduction

Adults 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 respiratoryrelated hospitalizations. Methods: We conducted a retrospective cohort study using claims data from Optum’s ClinformaticsÒ 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. Conclusions: Pooled 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. Adults 65 years and older (hereinafter referred to as seniors) are at greater risk for complications following influenza infection compared with younger adults, due in part to immunosenescence and increased comorbid conditions, leading to decreased vaccine efficacy and increased severity of influenza-related complications.

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Conclusion