Fig. 1From: Antibodies against 1940s era a/H1N1 influenza strains a/Weiss/43 and a/FM/1/47 and heterotypic responses after seasonal vaccination of an elderly Spanish populationPercentage of individuals showing pre-vaccination protective Abs against 1940s era A/H1N1 strains, A/H1N1 vaccine strains, and the A/H1N1pdm09 subtype during the whole study period and in each IVC (influenza vaccine campaign)Back to article page