Figure 8From: Levels of diphtheria and tetanus specific IgG of Portuguese adult women, before and after vaccination with adult type Td. Duration of immunity following vaccinationAntidiphtheria toxin IgG (ADT IgG) levels, by time since last dose of diphtheria-toxoid, in pre-vaccination sera of women who had been vaccinated with diphtheria-toxoid (Group A). Regression line (stippled) and threshold level of 100 mIU/ml.Back to article page