Figure 4
The percentage of patients with a positive immune response, that is seroconversion, (defined as prevaccination titers <10 and postvaccination HI titers ≥40 or a ≥4-fold increase in HI titers) following vaccination against H1N1 influenza stratified according to age (18 to 60 years and ≥ 60 years). The dashed lines denote seroconversion levels in healthy individuals when sufficient protection against infection is assumed (EU Committee of Human Medicinal Production criteria; CHMP). HI, hemagglutination inhibition.