Improved Immune Response Against Influenza A Viruses With Receipt of a Recombinant Influenza Vaccine in Healthcare Personnel With Prior Low Antibody Response to Egg-Based Influenza Vaccines, Israel, 2019–2020

Background: Adult studies have shown that quadrivalent recombinant influenza vaccines (RIV4) induce a higher antibody response than quadrivalent egg-based inactivated influenza vaccines (IIV4). Methods: Healthcare personnel (HCP) from a 2018–2019 cohort study that assessed IIV4 immunogenicity in Israel were recruited into a 2019–2020 randomized trial of RIV4 and IIV4. 2018–2019 low titer low responders (LTLRs) had pre-vaccination hemagglutination inhibition antibody titers ≤1:40 and <4-foldrise post-vaccination. We assessed whether RIV4 versus IIV4 receipt in the 2019–2020 season improved response among 2018–2019 LTLRs using logistic regression adjusted for employment hospital. Results: Of 228 HCP classified as 2018–2019 LTLRs, 2019–2020 RIV4 recipients were 3.6 (95% CI: 1.2–11.4) and 8.3 (95% CI: 3.0–26.3) times as likely to become a non-LTLR against influenza A(H1N1)pdm09 and cell-derived A(H3N2) vaccine components compared to IIV4 recipients. Conclusions: RIV4 had improved immunogenicity against influenza A viruses among previously classified low vaccine responder HCP, highlighting how recombinant influenza vaccines could improve antibody responses against influenza A for HCP at risk for poor influenza antibody response.