Studies on Diphtheria-Pertussis-Tetanus Combined Immunization in Children

Abstract

Summary The immune responses produced by the primary course of DPT vaccination were analyzed on the basis of known variables of the population under study. Observations extended over one year after the last dose show that the pre-existence of latent diphtheria immunity interfered with the speed of tetanus antitoxin response, and the magnitude and maintenance of pertussis agglutinin response. The tetanus antitoxin response was most seriously affected one month after the second dose, when the solid protection ratio between the normal and the diphtheriaimmune group was 87.0%:34.4%. The pertussis agglutinin response was most seriously affected one year after the third dose, with a solid protection ratio of 50.0%:13.8% between the groups. The data show that throughout the primary vaccination course, children younger than 24 months gave better diphtheria and tetanus antitoxin responses than the older children under a fixed dosage. Older children gave stronger pertussis agglutinin response than the younger children after the first dose, but weaker response after the third dose. Sex played no role in the immune responses to primary DPT vaccination.