Residual immunity in older people against the influenza A(H1N1) – recent experience in northern Spain
Pérez-Trallero, E and Piñeiro, L and Vicente, D and Montes, M and Cilla, G, Eurosurveillance, 14, 19344 (2009), https://doi.org/10.2807/ese.14.39.19344-en