H1N1 antibody persistence 1 year after immunization with an adjuvanted or whole-virion pandemic vaccine and immunogenicity and reactogenicity of subsequent seasonal influenza vaccine: a multicenter follow-on study.
Walker WT., de Whalley P., Andrews N., Oeser C., Casey M., Michaelis L., Hoschler K., Harrill C., Moulsdale P., Thompson B., Jones C., Chalk J., Kerridge S., John TM., Okike I., Ladhani S., Tomlinson R., Heath PT., Miller E., Faust SN., Snape MD., Finn A., Pollard AJ.
BACKGROUND: We investigated antibody persistence in children 1 year after 2 doses of either an AS03(B)-adjuvanted split-virion or nonadjuvanted whole-virion monovalent pandemic influenza vaccine and assessed the immunogenicity and reactogenicity of a subsequent dose of trivalent influenza vaccine (TIV). METHODS: Children previously immunized at age 6 months to 12 years in the original study were invited to participate. After a blood sample was obtained to assess persistence of antibody against swine influenza A/H1N1(2009) pandemic influenza, children received 1 dose of 2010/2011 TIV, reactogenicity data were collected for 7 days, and another blood sample was obtained 21 days after vaccination. RESULTS: Of 323 children recruited, 302 received TIV. Antibody persistence (defined as microneutralization [MN] titer ≥1:40) 1 year after initial vaccination was significantly higher in the AS03(B)-adjuvanted compared with the whole-virion vaccine group, 100% (95% confidence interval [CI], 94.1%-100%) vs 32.4% (95% CI, 21.5%-44.8%) in children immunized <3 years old and 96.9% (95% CI, 91.3%-99.4%) vs 65.9% (95% CI, 55.3%-75.5%) in those 3-12 years old at immunization, respectively (P < .001 for both groups). All children receiving TIV had post-vaccination MN titers ≥1:40. Although TIV was well tolerated in all groups, reactogenicity in children <5 years old was slightly greater in those who originally received AS03(B)-adjuvanted vaccine. CONCLUSIONS: This study provides serological evidence that 2 doses of AS03(B)-adjuvanted pandemic influenza vaccine may be sufficient to maintain protection across 2 influenza seasons. Administration of TIV to children who previously received 2 doses of either pandemic influenza vaccine is safe and is immunogenic for the H1N1 strain.