Immunogenicity and safety of high-dose quadrivalent influenza vaccine in older adults in Taiwan: A phase III, randomized, multi-center study.

High-dose influenza vaccine offers better protection against influenza/associated complications compared with standard-dose formulation. We evaluated immunogenicity and safety of high-dose influenza vaccine (QIV-HD) and standard-dose (QIV-SD) in older adults (≥ 65 years) in Taiwan. This was a phase III, randomized, modified double-blind, active-controlled, multi-center, descriptive study in older adults. Participants (N = 165) were randomized 1:1 to receive QIV-HD or QIV-SD vaccine (clinicaltrials.gov#NCT04537234). For all four influenza strains, geometric means titers (GMTs) of hemagglutination inhibition were higher for the QIV-HD than QIV-SD with adjusted GMT ratios (95 % CI) of 2.65 (1.87-3.75) for A/H1N1; 1.76 (1.31-2.38) for A/H3N2; 2.60 (1.90-3.56) for B/Victoria; and 2.01 (1.57-2.56) for B/Yamagata. The seroconversion was higher for QIV-HD than QIV-SD with similar safety profiles across both groups. QIV-HD was highly immunogenic for four influenza strains and have acceptable safety profile in older adults aged ≥ 65 years in Taiwan.