Table 1. The antibody geometric mean titers with 95% confidencial intervals (CI).
| Virus strain | group | Amino acid changes* | Geometric mean (95%CI) |
| A/California/7/09 E2 | California-like | 28.5 (22.6–35.9) | |
| A/California/7/09 M3 | California-like | 24.0 (19.4–29.7) | |
| A/Finland/554/09 | California-like | I321V, S451N | 27.8 (22.9–33.7) |
| A/Finland/653/09 | I/2009 | S203T, I321V, N444K | 31.5 (25.9–38.4) |
| A/Finland/694/09 | I/2009 | S203T,N125D,N156K, I321V, N444K | 14.7 (12.8–16.8) |
| A/Finland/619/09 | II/2009 | S203T, D222E, I321V | 33.9 (27.6–41.6) |
| A/Finland/634/09 | II/2009 | S203T,P137S, D222E, I321V | 26.4 (21.3–32.6) |
| A/Finland/686/09 | III/2009 | S203T, I321V,L314MA493T | 28.8 (23.6–35.2) |
| A/Finland/698/09 | III/2009 | S203T, S74N, I321V, L314 | 21.1 (17.8–25.1) |
| A/Finland/618/09 | IV/2009 | S203T, S162R | 22.6 (18.7–27.4) |
| A/Finland/692/09 | IV/2009 | S203T, A73T | 32.9 (26.9–40.2) |
The antibody titers of a set of 120 sera were analyzed against A/California/07/2009 virus and thirteen pandemic influenza A(H1N1) 2009 viruses isolated in Finland during 2009–2010 and 2010–2011 seasons. The group of each virus is determined by sequencing the hemagglutinin gene and it's location in the phylogenetic tree. *Amino acid changes, which locate in the surface of the HA molecule, as compared to A/California/7/09 virus.