Humoral and Cellular Immunity Induced by Adjuvanted and Standard Trivalent Influenza Vaccine in Older Nursing Home Residents.

Background Despite wide use of adjuvanted influenza vaccine in nursing home residents (NHR), little immunogenicity data exist for this population. Methods We collected blood from NHR (n = 85) living in nursing homes participating in a cluster randomized clinical trial comparing MF59-adjuvanted trivalent inactivated influenza vaccine (aTIV) with nonadjuvanted vaccine (TIV) (parent trial, NCT02882100). NHR received either vaccine during the 2016–2017 influenza season. We assessed cellular and humoral immunity using flow cytometry and hemagglutinin inhibition, antineuraminidase (enzyme-linked lectin assay), and microneutralization assays. Results Both vaccines were similarly immunogenic and induced antigen-specific antibodies and T cells, but aTIV specifically induced significantly larger 28 days after vaccination (D28) titers against A/H3N2 neuraminidase than TIV. Conclusions NHRs respond immunologically to TIV and aTIV. From these data, the larger aTIV-induced antineuraminidase response at D28 may help explain the increased clinical protection observed in the parent clinical trial for aTIV over TIV in NHR during the A/H3N2-dominant 2016–2017 influenza season. Additionally, a decline back to prevaccination titers at 6 months after vaccination emphasizes the importance of annual vaccination against influenza. Clinical Trials Registration NCT02882100. [ABSTRACT FROM AUTHOR]