Safety and Immunogenicity of a Subvirion Monovalent Unadjuvanted Inactivated Influenza A(H3N2) Variant Vaccine in Healthy Persons ≥18 Years Old.
2015 Aug 15
Journal Article
Authors:
Secondary:
J Infect Dis
Volume:
212
Pagination:
552-61
Issue:
4
PMID:
25649171
Keywords:
Adolescent; Adult; Aged; Antibodies, Viral; B-Lymphocytes; Female; Humans; Immunoglobulin G; Influenza A Virus, H3N2 Subtype; Influenza Vaccines; Influenza, Human; Male; Middle Aged; Young Adult
Abstract:
<p>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 µg 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-µg 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.CLINICAL TRIALS REGISTRATION: NCT01746082.</p>