Table 3. Predominant genetic groups of circulating viruses compared to influenza vaccine-recommended viruses.
| Influenza virus | 2017 Southern Hemisphere influenza season | 2017–18 Northern Hemisphere influenza season | 2018 Southern Hemisphere influenza season | |||
|---|---|---|---|---|---|---|
| Genetic group of vaccine-recommended virus | Genetic group that predominated in analysisb (May-Sep 2017) | Genetic group of vaccine- recommended virus | Genetic group that predominated in analysisb (Oct 2017—Apr 2018) | Genetic group of vaccine-recommended virus | Genetic group that predominated in analysisb (May-Sep 2018) | |
| H1pdm09 | 6B.1 | 6B.1 | 6B.1 | 6B.1 | 6B.1 | 6.B1. |
| H3 | 3C.2a | 3C.2a2 | 3C.2a | 3C.2a2 | 3C.2a1 | 3C.2a2 |
| B Victoriaa | V1A | V1A | V1A | V1A.1 | V1A | V1A.1 |
| B Yamagataa | Y3 | Y3 | Y3 | Y3 | Y3 | Y3 |
a The lineage of the influenza B virus included in the 2017 Southern Hemisphere and 2017–18 Northern Hemisphere trivalent vaccine was B/Victoria, and the lineage of the influenza B virus included in the 2018 Southern Hemisphere trivalent vaccine was B/Yamagata
b Among sequences from participating countries (Argentina, Brazil, Chile, Colombia, Costa Rica, Ecuador, Mexico, Paraguay, Peru, Uruguay)