Weighted age-specific geometric mean IgG concentrations of diphtheria antibody in the national sample of the 1995/1996 serosurvey (n = 7691) and 2006/2007 serosurvey (n = 6383).

<p>The error bars represent the 95% confidence intervals. Year of birth indicates median year of birth corresponding to the defined age category. The dashed horizontal line represents the minimum level of protection of 0.01 IU/ml. The textbox shows changes in the National Immunization Program.