DTP-associated reactions: an analysis by injection site, manufacturer, prior reactions, and dose.

Local and less serious systemic reactions are frequent following immunization with diphtheria-tetanus-pertussis (DTP) vaccine. The effects of injection site, manufacturer, previous reactions, and dosage reduction upon subsequent reactions to DTP immunization were investigated. Local reactions, notably pain and swelling, were less common when the immunization was given in the buttocks than in the thigh. No injection site was consistently associated with lower systemic reaction rates. There was no significant difference in the rate of more serious reactions by vaccine manufacturer. Differences in rates of less serious reactions by manufacturer were observed but seemed to be related to vaccine lot differences rather than the specific vaccines. In a subset of 772 children, in whom data regarding sequential reactions were available, it was noted that all three reactions investigated--local redness, temperature greater than or equal to 39 degrees C, and persistent crying longer than one-half hour--were two to three times more frequent on a subsequent immunization when present on a prior vaccination than if not present on a prior vaccination than if not present previously. One hundred children received a half dose of DTP vaccine because of a less serious reaction associated with prior immunization. In all instances, they had significantly less serious local reactions as well as notable differences in temperature, drowsiness, and persistent crying.