Evaluation of influenza vaccine-immunogenicity in cell-mediated immunity.

The immunological effect of influenza vaccines cannot be evaluated accurately using an antibody titer. Therefore, we used a new method that measures cell-mediated immunity to investigate changes in the amount of interferon-gamma (IFN-γ) produced after vaccination in response to the vaccine antigen. The study was conducted during the 2014-2015 influenza season in 23 adults, using a vaccine that contained three types of antigen. The IFN-γ level increased by at least 1.5 times in 65% (15/23) of cases in response to the H1N1 antigen, in 57% (13/23) of cases in response to the H3N2 antigen, and in 57% (13/23) of cases in response to the B antigen. During the study period, 4 subjects developed type A influenza. Our data showed that the IFN-γ level did not increase by 1.5 times in these subjects. We propose that the efficacy of influenza vaccines may be evaluated by measuring changes in the level of IFN-γ produced in response to influenza vaccine.