Immunogenicity of FDA DTP versus WHO DTP

The aim of this report was to study the immunogenicity of three doses of DTP in six-week-old Saudi infants when given either as World Health Organization (WHO) DTP or Federal Drug Administration (FDA) DTP formula. As part of the Haemophilus influenzae type b immunization research protocol, six-week-old infants were randomized into three groups to receive three doses of HbOC and WHO DTP formula, HbOC and FDA DTP formula, or in a control group to receive the usual vaccines without HbOC, at six weeks, three months and five months. Antibody levels for PRP, tetanus, diphtheria and pertussis were measured after the third dose. The results of diphtheria, pertussis and tetanus are presented in this paper. After three doses, no difference was found between anti-PRP when given with either FDA DTP or WHO DTP formula. Also anti-tetanus and anti-diphtheria antibodies were significantly higher in the group vaccinated with HbOC and FDA DTP formula, compared to children vaccinated with WHO DTP formula. No negative interactions with other vaccines were observed after the third dose. Conclusion. Although diphtheria and tetanus antigens in the FDA formula are half the concentration in the WHO formula, they are more antigenic. There is a need for methods of potency assay to be re-evaluated.