Abstract
Background
Antibody responses to non-egg-based standard-dose cell-culture influenza vaccine (containing 15 µg hemagglutinin (HA)/component) and recombinant vaccine (containing 45 µg HA/component) during consecutive seasons have not been studied in the United States.
Methods
In a randomized trial of immunogenicity of quadrivalent influenza vaccines among healthcare personnel (HCP) aged 18–64 years over two consecutive seasons, HCP who received recombinant-hemagglutinin (RIV) or cell-culture-based vaccine (ccIIV) during the first season (Y1) were re-randomized the second season of 2019-2020 (Y2) to receive ccIIV or RIV, resulting in four ccIIV-RIV combinations. In Y2, hemagglutination inhibition (HI) antibody titers against reference cell-grown vaccine viruses were compared in each ccIIV-RIV group with titers among HCP randomized both seasons to receive egg-based, standard-dose inactivated influenza vaccine (IIV), using geome tric mean titer (GMT) ratios of Y2-post-vaccination titers.
Results
Y2 data from 414 HCPs were analyzed per-protocol. Compared to 60 IIV/IIV recipients, 74 RIV/RIV and 106 ccIIV/RIV recipients showed significantly elevated GMT ratios (Bonferroni corrected
P <.007) against all components except A (H3N2). Post-vaccination GMT ratios for ccIIV/ccIIV and RIV/ccIIV were not significantly elevated compared to IIV/IIV except for RIV/ccIIV against A(H1N1)pdm09.
Conclusions
In adult HCPs, receipt of RIV two consecutive seasons or the second season was more immunogenic than consecutive egg-based IIV for three of the four components of quadrivalent vaccine. Immunogenicity of ccIIV/ccIIV was similar to that of IIV/IIV. Differences in hemagglutinin antigen content may play a role in immunogenicity of influenza vaccination in consecutive seasons.
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