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Safety and Immunogenicity of a Subvirion Monovalent Unadjuvanted Inactivated Influenza A(H3N2) Variant Vaccine in Healthy Persons >/=18 Years Old


Journal Article

Keitel, W.A.; Jackson, L.A.; Edupuganti, S.; Winokur, P.L.; Mulligan, M.J.; Thornburg, N.J.; Patel, S.M.; Rouphael, N.G.; Lai, L.; Bangaru, S.; McNeal, M.M.; Bellamy, A.R.; Hill, H.R.; Group, T.V.T.E.U.H.3Nv

J Infect Dis




H3N2 variant; immune responses; immunization; influenza; pandemic

BACKGROUND: Variant influenza A(H3N2) viruses (H3N2v) have transmitted recently from pigs to humans in the United States. Vaccines strategies are needed. METHODS: Healthy adults received 2 doses of subvirion H3N2v vaccine (15 microg of hemagglutinin/dose) 21 days apart in this open-label trial. Serum hemagglutination inhibition (HAI) and neutralizing (Neut) antibody (Ab) titers were measured before and 8 and 21 days after each dose. Memory B-cell (MBC) responses were assessed. RESULTS: Vaccine was well tolerated. A total of 40% of subjects had an HAI Ab titer of >/=40 before vaccination. Eight-seven percent (95% confidence interval [CI], 79%-93%) and 73% (95% CI, 63%-81%) of subjects 18-64 years old (98 subjects) and >/=65 years old (90 subjects), respectively, had an HAI titer of >/=40 21 days after dose 1 (P = .01); 51% (95% CI, 41%-61%) and 52% (95% CI, 41%-62%) of younger and older subjects, respectively, developed >/=4-fold rises in titer (P = not significant). Neut Ab response patterns were similar. Geometric mean titers were higher in younger subjects. Dose 2 provided no significant enhancement in responses. Cross-reactive MBCs were detected before vaccination and expanded after vaccination. Preexisting H3N2v-specific MBCs positively correlated with early increases in vaccine-induced Ab. CONCLUSIONS: In most healthy adults, one 15-microg dose of vaccine elicited levels of HAI Abs associated with protection. Studies in children and elderly individuals are indicated to define the immunization needs of these groups.

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