Gene expression profiles associated with humoral response to influenza vaccine, Vaxigrip, in young and elderly subjects of Chinese ethnicity in Singapore

While studying influenza vaccine-induced responses, the elderly are typically considered as a homogeneous population. However, chronological age alone is insufficient in defining immune responsiveness of individuals. In this study, a stratified cohort of elderly (65 year old and above) and young (below 35 year old) individuals was recruited to study the heterogeneity of influenza vaccine-induced responses and identify innate signatures including gene expression profiles defining vaccine immunogenicity. The study was conducted in Singapore, a tropical setting without well-defined influenza seasons. The gene expression profiles are from 143 elderly (92 females, 51 males) and 29 young (18 females, 11 males) subjects of Chinese ethnicity in Singapore who were administered trivalent inactivated 2013-14 seasonal influenza vaccine (Vaxigrip) containing B/Massachusetts, A/H1N1/California and A/H3N2/Texas strains. Gene expression was interrogated in PBMCs collected from the vaccines prior to vaccination (day 0) and on days 2, 7 and 28 post-vaccination. Non-institutionalized community dwelling subjects were recruited as part of a phase IV clinical trial of Sanofi Pasteur’s Vaxigrip influenza vaccine approved by the National University of Singapore Institutional Review Board and registered at clinicaltrials.gov under the registration number NCT03266237. Volunteers were excluded if they had received an influenza vaccine within the 6 months preceding the trial vaccination or planned influenza vaccination during the trial. Those with suspected congenital or acquired immunodeficiency; or in receipt of immunosuppressive therapy such as anti-cancer chemotherapy or radiation therapy within the preceding 6 months; or on long-term systemic corticosteroid therapy (prednisone or equivalent for more than 2 consecutive weeks within the past 3 months) were also excluded. All volunteers provided written informed consent for the administration of seasonal influenza vaccine.