Primary immunization with diphtheria-tetanus toxoids vaccine and diphtheria-tetanus toxoids-pertussis vaccine adsorbed: comparison of schedules

Abstract

In a double blind study patients were randomly divided into two groups. All patients received an initial immunization with diphtheria-tetanus toxoids-pertussis (DTP) vaccine at 2 months of age. One population received diphtheria-tetanus toxoids (DT pediatric) vaccine at the time of the second immunization at 4 months of age and DTP vaccine at 6 months (DTP-DT-DTP). In a second group DTP vaccine was administered as the second immunization and DT (pediatric) vaccine was given at the 6-month visit (DTP-DTP-DT). There was a significantly increased incidence and severity of adverse reactions associated with DTP vaccine when contrasted with responses observed after DT vaccine; differences were apparent whether the vaccine was administered as the second or the third immunization. All patients had serologic evidence of protection to diphtheria and tetanus following completion of either primary series. The geometric mean titer of pertussis agglutinins was similar in the two study groups 2 months after the second DTP immunization but was significantly higher in the DTP-DT-DTP group at 1 to 2 months after the completion of the primary immunization series (P less than 0.01). Both groups, however, were significantly lower than the comparable geometric mean titer measured after a series of three DTP inoculations (7.51, log2) (P less than 0.01). This study supports the recommendation that three immunizations of DTP be administered in the first year of life.