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.

Cluster-randomized Trial of Adjuvanted Versus Nonadjuvanted Trivalent Influenza Vaccine in 823 US Nursing Homes.

BACKGROUND: Influenza leads in preventable infection-related hospitalization in nursing home (NH) residents. The adjuvanted trivalent influenza vaccine (aTIV) is more immunogenic than similarly dosed nonadjuvanted trivalent influenza vaccine (TIV), and observational studies suggest aTIV better prevents hospitalizations in older adults. We prospectively tested this in an NH setting. METHODS: NHs with ≥50 long-stay residents aged ≥65 years were randomized to offer aTIV or TIV for residents for the 2016-2017 influenza season. Using intent-to-treat resident-level analysis with Cox proportional hazards regression models adjusted for clustering by facility and a priori baseline covariates (eg, age, heart failure, and facility-level characteristics), we assessed relative aTIV:TIV effectiveness for hospitalization (ie, all-cause, respiratory, and pneumonia and influenza [P&I]). RESULTS: We randomized 823 NHs, housing 50 012 eligible residents, to aTIV or TIV. Residents were similar between groups by age (mean, ~79 years), heart failure, lung disease, and influenza and pneumococcal vaccine uptake, except aTIV homes housed fewer Black residents (14.5 vs 18.9%). Staff vaccine uptake was similar (~55%). P&I and all-cause resident hospitalization rates were lower (adjusted HR [aHR], .80 [95% CI, .66-.98; P = .03] and .94 [.89-.99; P = .02], respectively) for aTIV versus TIV, while the respiratory hospitalization rate was similar, in a season where vaccine effectiveness was considered poor. CONCLUSIONS: aTIV was more effective than TIV in preventing all-cause and P&I hospitalization from NHs during an A/H3N2-predominant season when TIV was relatively ineffective. CLINICAL TRIALS REGISTRATION: NCT02882100.