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Table 3 Identification of amino acid substitutions in H1 antigenic sites of pH1N1 viruses. Antigenic sites of HA sequences were compared to vaccine strains A/California/07/2009. Amino acids in italics indicate amino acids that differ from vaccine sequence. Bold amino acids denote amino acid changes found in vaccine strain recommended for subsequent season (A/Michigan/45/2015). A/California/07/2009 was used in influenza vaccine composition since the emergence of pandemic H1N1 in 2009 before being replaced by A/Michigan/45/2015 in 2016. Similarity of antigenic sites between vaccine strains and circulating viruses is shown as percentages in the last column

From: Epidemiological and genetic characterization of pH1N1 and H3N2 influenza viruses circulated in MENA region during 2009–2017

H1 Similarity to pH1N1 vaccine strain (%)
  Sa Sb Ca
179 180 202 220
California/2009 S K S S Sa Sb Ca
2016 N Q T T 84.6 91.7 94.7
Michigan/2015a N Q T T  
  1. aA/Michigan/45/2015 vaccine was recommended to be used in 2016–2017 season, however, only 3 sequences were depicted in NCBI-IRD from MENA region during 2017 therefore sequences isolated in 2016 were used for comparison purpose