Seasonal influenza vaccination does not effectively expand H2 cross-reactive antibodies in humans

Influenza viruses cause millions of infections and hundreds of thousands of deaths every year. Influenza virus vaccinations are produced every year and contain H1N1 and H3N2 influenza A viruses and either one or two influenza B viruses. In this study, we examined the effects of seasonal influenza vaccinations in people on both circulating serum antibody titers and memory B-cell activation to H2Nx influenza viruses. In addition to evaluating the human cohort as a whole, participants were also divided into three separate groups based upon their likelihood of being either exposed to or imprinted with H2N2 influenza viruses in the 1950s and 1960s. While participants born after H2N2 influenza viruses left the human population had lower HAI, ELISA and neutralizing antibody titers to these viruses, a select number of cross-reactive antibodies to some of the H2 HA proteins were boosted after seasonal influenza vaccination. However, these results varied and were not consistent by age group or specific H2 HA protein. Overall, seasonal influenza vaccination did not significantly expand cross-reactive antibodies to H2 HA antigens.