Figure 3

Seroconversion rates 21 days after QIV (A) or TIV (B) in the per-protocol immunogenicity cohort. QIV, inactivated quadrivalent influenza vaccine; TIV, inactivated trivalent influenza vaccine; Seroconversion rate defined as the proportion with antibody titer <1:10 at baseline and with post-vaccination titer of ≥1:40, or pre-vaccination titer of ≥1:10 and a ≥4-fold post-vaccination increase in titer; European Union Committee for Medicinal Products for Human Use (CHMP) licensure threshold for seroconversion: >40% in the 18–60 years group, and >30% in the >60 years group [17].