RT Journal Article SR Electronic(1) A1 Pérez-Trallero, E A1 Piñeiro, L A1 Vicente, D A1 Montes, M A1 Cilla, G YR 2009 T1 Residual immunity in older people against the influenza A(H1N1) – recent experience in northern Spain JF Eurosurveillance VO 14 IS 39 SP 19344 OP DO https://doi.org/10.2807/ese.14.39.19344-en UL https://www.eurosurveillance.org/content/10.2807/ese.14.39.19344-en