Abstract
There are significant antigenic differences within subtypes that change over time as these viruses evolve, and this requires a semi-annual review and frequent update of vaccine strain candidates for human seasonal influenza vaccines. The degree of relatedness between the strains contained in the seasonal vaccine and the drifted strains that are isolated the following year is assessed through cross haemagglutination inhibition (HI) tests. If the results of these tests suggest that cross HI levels are low, the vaccine is updated to include the most recent strains. We reasoned that if a semi-annual review of the antigenic characteristics of human H1 and H3 viruses is necessary
Highlights
Influenza A viruses all originate from aquatic birds, which are their natural reservoir
We reasoned that if a semi-annual review of the antigenic characteristics of human H1 and H3 viruses is necessary due to antigenic drift resulting from immunologic pressure, it was possible that contemporary avian H1 and H3 viruses would not be cross-reactive with contemporary seasonal influenza A viruses
We tested by haemagglutination inhibition (HI) 30 human serum specimens, obtained 3–5 weeks after the administration of the 2006–2007 seasonal vaccine, against A/Wisconsin/67/2005/ H3N2, A/New Caledonia/20/99/H1N1, and A/Singapore/57/H2N2 to establish serological titres to human influenza viruses
Summary
Influenza A viruses all originate from aquatic birds, which are their natural reservoir. Any emerging pandemic virus will be different antigenically from both human vaccine virus strains and contemporary human viruses, and so the human population will be immunologically naıve to a significant degree to the new virus before it spreads widely.
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