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
| 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 | |||
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