Annual influenza vaccination is the most effective strategy available to combat seasonal influenza, but data suggest that repeated vaccination hinders cross-reactive CD8+ T-cell immunity, potentially increasing susceptibility during vaccine mismatch or a pandemic.
In a study carried out in 2010–2013, 25 healthcare workers received a single AS03-adjuvanted H1N1pdm09 vaccine in 2009, and then either repeated annual vaccination or no further vaccination. Blood samples were taken before the influenza season/vaccination to assess antibody and T-cell responses.
In both the repeated- and single-vaccination groups, antibody levels against H1N1pdm09 remained above the protective threshold in most people. CD4+ T cell responses remained stable in the repeated group but declined significantly in the single-vaccination group. Furthermore, the quality of CD4+ responses was higher in the repeated group than the single group. CD8+ T cell responses remained stable in both groups.
Reporting in The Journal of Infectious Diseases, the researchers said the findings suggest that there are immunological benefits from repeated annual vaccination