Trivalent influenza vaccine-induced antibody response to circulating influenza a (H3N2) viruses in 2010/11 and 2011/12 seasons

Abstract

To evaluate antibody response induced by trivalent inactivated influenza vaccine (TIV) against circulating influenza A(H3N2) strains in healthy adults during the 2010/11 and 2011/12 seasons, a hemagglutination-inhibition (HI) assay wasutilized to calculate geometric mean antibody titer (GMT), seroprotection rate (post vaccination HI titers of ≥ 1 :40), andseroresponse rate (4-fold increase in antibody level). In the 2010/11 season, GMT increased 1.8- to 2.0-fold following thefirst dose of TIV against 3 circulating strains and 2.2-fold following the second compared to before vaccination. Theseroresponse rate ranged from 22% to 26% following the first dose of TIV and from 31% to 33% following the second(n = 54). The seroprotection rate increased from a range of 6% to 13% to a range of 26% to 33% following the firstdose of TIV and to a range of 37% to 42% following the second (n = 54). In the 2011/12 season, GMT increased 1.4-foldagainst A/Osaka/110/2011 and 1.8-fold against A/Osaka/5/2012. For A/Osaka/110/2011, the seroresponse rate was 29%,and the seroprotection rate increased from 26% to 55% following vaccination (n = 31). For A/Osaka/5/2012, theseroresponse rate was 26%, and the seroprotection rate increased from 68% to 84% following vaccination (n = 31). HIassays with reference antisera demonstrated that the strains in the 2011/12 season were antigenically distinct fromvaccine strain (A/Victoria/210/2009). In conclusion, the vaccination increased the seroprotection rate against circulatingH3N2 strains in the 2010/11 and 2011/12 seasons. Vaccination of TIV might have potential to induce reactive antibodiesagainst antigenically distinct circulating H3N2 viruses.