Antibody responses against influenza A decline with successive years of annual influenza vaccination
Sheena G. Sullivan, Arseniy Khvorov, Louise Carolan, Leslie Dowson, A. Jessica Hadiprodjo, Stephany Sánchez‐Ovando, Yi Liu, Vivian Leung, David Hodgson, Christopher C. Blyth, Marion Macnish, Allen Cheng, Michelle Haugenauer, Julia Clark, Sonia Dougherty, Kristine Macartney, Archana Koirala, Ameneh Khatami, Ajay Jadhav, Helen Marshall, Kathryn E. Riley, Peter Wark, Catherine Delahunty, Kanta Subbarao, Adam J. Kucharski, Annette Fox
Abstract
Influenza vaccine effectiveness and immunogenicity can be compromised with repeated vaccination. We assessed immunological markers in a cohort of healthcare workers (HCW) from six public hospitals around Australia during 2020-2021. Sera were collected pre-vaccination and ~14 and ~180 days post-vaccination and assessed in haemagglutination inhibition assay against egg-grown vaccine and equivalent cell-grown viruses. Responses to vaccination were compared by the number of prior vaccinations. Baseline sera were available for 595 HCW in 2020 and 1031 in 2021. 5% had not been vaccinated during five years prior to enrolment and 55% had been vaccinated every year. Post-vaccination titres for all vaccine antigens were lowest among HCW vaccinated in all 5-prior years and highest among HCW with 0 or 1 prior vaccinations, even after adjustment. This was observed for both influenza A subtypes and was dependent on pre-vaccination titre. Expanded cohorts are needed to better understand how this translates to vaccine effectiveness.