Immunogenicity and reactogenicity of high- vs. standard-dose trivalent inactivated influenza vaccine in healthcare workers: a pilot randomized controlled trial

To compare immunogenicity, reactogenicity and acceptability of high- and standard-dose trivalent inactivated influenza vaccine (HDTIV, SDTIV) in 18- to 64-year-olds. We randomized 18- to 64-year-olds to HDTIV or SDTIV in two consecutive years. We collected serum on days 0 and 21, measured haemagglutination inhibition geometric mean titres (GMT) and compared seroconversion, day 21 titres, seroprotection, reactogenicity and acceptability. Immunogenicity was evaluable in 42 of 47 2014 participants, all 33 both-year participants and 87 of 90 2015-only participants. First-dose HDTIV recipients experienced seroconversion more frequently than SDTIV recipients to A(H3N2) in 2014 (13/21, 62% vs. 4/21, 19%, p 0.01) and to all vaccine strains in 2015: (A(H1N1): 24/42, 57% vs. 15/59, 25%; A(H3N2): 42/42, 100% vs. 47/59, 80%; B: 25/42, 60% vs. 13/59, 22%; all p