Scientific Publications by FDA Staff

Clin Infect Dis 2019 May 30;68(12):2067-78

Neutralizing antibody responses to homologous and heterologous H1 and H3 influenza A strains after vaccination with inactivated trivalent influenza vaccine vary with age and prior year vaccination.

Wang W, Chen Q, Ford-Siltz LA, Katzelnick LC, Parra GI, Song HS, Vassell R, Weiss CD

BACKGROUND: Prior influenza immunity influences homologous neutralizing antibody responses elicited by inactivated influenza vaccines (IIV), but neutralizing antibody responses to heterologous strains have not been extensively characterized. METHODS: We analyzed neutralizing antibody titers in individuals ages 1-88 who received the 2009-2010 season IIV before 2009 pandemic H1N1 infection or vaccination in a prior clinical trial. Neutralization titers to homologous and heterologous past, recent, and advanced H1 and H3 strains, as well as H2, H5, and H7 strains, were measured using influenza hemagglutinin pseudoviruses. We performed exploratory analyses based on age, prior year IIV, and pre-vaccination titer, without controlling for Type I error. RESULTS: IIV elicited neutralizing antibodies to past and advanced H1 and H3 strains, as well as to an H2 strain in individuals likely infected early in life. Neutralization of avian subtype viruses was rare, and imprinting of neutralization responses to novel avian subtype viruses based on influenza group was not seen. Compared to adults, children had higher seroresponse rates to homologous and heterologous strains, and their sera generated larger antigenic distances among strains. Seroresponse rates to homologous and heterologous strains were lower in subjects vaccinated with prior year IIV, though post-immunization titers were generally high. CONCLUSIONS: IIV elicited neutralizing antibodies to heterologous H1 and H3 strains in all ages groups, but titers and seroresponse rates were usually higher in children. Prior year vaccination with the same strains tended to blunt IIV neutralization responses to all strains in young and old age groups, yet post-immunization titers were high.