Reduced cross-protection against influenza A(H3N2) subgroup 3C.2a and 3C.3a viruses among Finnish healthcare workers vaccinated with 2013/14 seasonal influenza vaccine Haveri, A and Ikonen, N and Julkunen, I and Kantele, A and Anttila, V J and Ruotsalainen, E and Nohynek, H and Lyytikäinen, O and Savolainen-Kopra, C, Eurosurveillance, 20, 21028 (2015), https://doi.org/10.2807/1560-7917.ES2015.20.5.21028