Table 3. Influenza viruses characterised by clade, amino acid substitutions and study site, six European studies, interim influenza season 2022/23 (n = 806).
| Characterised viruses | Clade | DK-H/DK-PCa | EU-PCb | EU-H | SC-H | ||||
|---|---|---|---|---|---|---|---|---|---|
| n | % | n | % | n | % | N | % | ||
| Influenza A(H1N1)pdm09 (n = 175) | n = 74 | n = 81 | n = 0 | n = 20 | |||||
| A/Guangdong Maonan/SWL1536/2019 | 6B.1A.5a.1 | 0 | NC | 1 | 1 | 0 | NC | 0 | NC |
| A/Victoria/2570/2019 | 6B.1A.5a.2 | 0 | NC | 0 | NC | 0 | NC | 0 | NC |
| A/Sydney/5/2021c | 6B.1A.5a.2 | 57 | 77 | 59 | 73 | 0 | NC | 0 | NC |
| A/Norway/25089/2022d | 6B.1A.5a.2 | 17 | 23 | 21 | 26 | 0 | 0 | 20 | NC |
| Influenza A(H3N2) (n = 570) | n = 93 | n = 444 | n = 18 | n = 15 | |||||
| A/Denmark/3264/2019 | 3C.2a1b.1a | 0 | NC | 0 | NC | 0 | NC | 0 | NC |
| A/Cambodia/e0826360/2020 | 3C.2a1b.2a.1 | 0 | NC | 0 | NC | 0 | NC | 0 | NC |
| A/Darwin/9/2021 | 3C.2a1b.2a.2 | 8 | 9 | 0 | NC | 0 | NC | 0 | NC |
| A/Slovenia/8720/2022e | 3C.2a1b.2a.2 | 40 | 43 | 113 | 25 | 4 | NC | 0 | NC |
| A/Bangladesh/4005/2020f | 3C.2a1b.2a.2 | 45 | 48 | 331 | 75 | 14 | NC | 15 | NC |
| Group (i) S156H + others | NA | 45 | NC | 296 | 89 | 13 | NC | 0 | NC |
| Group (ii) D53N + others | NA | 0 | NC | 35 | 11 | 1 | NC | 0 | NC |
| Influenza B/Victoria (n = 82) | n = 22 | n = 60 | n = 0 | n = 0 | |||||
| B/Washington/02/2019 | V1A.3 | 0 | NC | 0 | NC | 0 | NC | 0 | NC |
| B/Netherlands/11267/2022 | V1A.3 | 0 | NC | 0 | NC | 0 | NC | 0 | NC |
| B/Cote d'Ivoire/948/2020 | V1A.3a.1 | 0 | NC | 0 | NC | 0 | NC | 0 | NC |
| B/Austria/1359417/2021 | V1A.3a.2 | 22 | NC | 60 | 100 | 0 | NC | 0 | NC |
DK-H: Denmark hospital study; DK-PC: Denmark primary care study; EU-H: European Union hospital multicentre VEBIS study; EU-PC: European Union primary care multicentre VEBIS study; NA: not applicable; NC: not calculated (percentages not shown where denominators < 60); SC-H: Scotland hospital study; VEBIS: Vaccine Effectiveness, Burden and Impact Studies.
a DK-H and DK-PC samples are combined.
b At time of writing, issues between linkage of epidemiological record identification (ID) numbers and sequencing ID numbers resulted in a low proportion of viruses included from two study sites within EU-PC.
c Harbouring the K54Q, A186T, Q189E, E224A, R259K and K308R amino acid mutations compared with the vaccine virus A/Victoria/2570/2019.
d Harbouring the A/Sydney/5/2021-like amino acid changes, and additionally P137S, K142R, D260E and T277A amino acid mutations compared with the vaccine virus A/Victoria/2570/2019.
e Harbouring the D53G, D104G and K276R amino acid mutations compared with the vaccine virus A/Darwin/9/2021.
f Harbouring the S156H amino acid mutation among others or the D53N amino acid mutation among others compared with the vaccine virus A/Darwin/9/2021.