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