The study investigates the rapid evolution of the influenza A virus in Shanghai, focusing on A/H1N1 and A/H3N2 strains from 2005 to 2008.
Key findings indicate significant antigenic differences between older and more recent A/H1N1 strains, linked to a specific amino acid mutation.
Results also reveal substantial antigenic drift in A/H3N2 strains, highlighting the need for updating the vaccine component for better effectiveness against recently circulating viruses.