Journal
PEDIATRIC INFECTIOUS DISEASE JOURNAL
Volume 23, Issue 9, Pages 852-856Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1097/01.inf.0000137566.87691.3b
Keywords
influenza vaccine; immunogenicity; neutralization; assay
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Background: Hemagglutination inhibition (HAI) assay is the standard method for evaluating inactivated influenza vaccines, but no standard assay has been established for evaluating live attenuated influenza vaccines (LAIV). LAW containing A/Beijing/262/95(H1N1) induced low serum HAI antibody responses to the antigenic variant, A/New Caledonia/20/99(H1N1) in a serologic study but provided protection against the A/New Caledonia-like viruses in a community study. Neutralization and HAI assays were compared by measuring H1N1 cross-reactive antibody responses to the LAW in children. Methods: Sera were collected from 50 children 1-8 years of age before vaccination and 4-6 weeks after each dose of the LAIV. Antibody titers to the 3 vaccine viruses were measured by the HAI assay, whereas antibody titers against the H1N1 vaccine virus (A/Beijing/262/95) and 2 H1N1 antigenic variants (A/Shenzhen/227/95 and A/New Caledonia/20/99) were measured by the HAI and neutralization assays. Results: Initially seronegative participants were more likely to develop HAI seroconversion responses to the 3 vaccine viruses than the baseline seropositive participants (77% versus 14% for H1N1, 100% versus 20% for H3N2, 100% versus 19% for 13, P<0.01, Fisher's exact test). For the H1N1 cross-reactive antibody responses, seroconversion rates measured by the neutralization assay were significantly higher than those measured by the HAI assay (95% versus 78%, P = 0.0485 for A/Beijing/262/95; 75% versus 24%, P<0.0001 for A/Shenzhen/227/95; 51% versus 5%, P<0.0001 for A/New Caledonia/20/99). Conclusions: The neutralization assay was more sensitive than the HAI assay for measuring H IN 1 antibody responses after vaccination of children with the LAW and may provide a better correlate of clinical protection provided by the LAIV.
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