DTP vaccine reactions: effect of prior reactions on rate of subsequent reactions.

It is generally presumed that children who have had reactions to diphtheria-tetanus-pertussis (DTP) immunization will be more likely to have similar reactions or more severe reactions upon subsequent immunization. To evaluate this contention, we studied the rates of selected reactions occurring within 48 hours of primary DTP immunization in 1,241 infants less than one year of age. Both local and systemic reactions were significantly more frequent following subsequent DTP immunization if present following a prior immunization. The rates of local reactions following subsequent DTP immunization as a function of previous reactions were as follows (no prior reactions/prior reaction): local redness greater than or equal to 2.5 cm, 12.5%/25.5% (p less than 0.0001); local swelling greater than or equal to 2.5 cm, 16.8%/29.0% (p less than 0.0001); local pain, 37.4%/56.4%; (p less than 0.0001). The rates of systemic reactions as a function of previous reactions were as follows (no prior reactions/prior reaction): drowsiness, 24.9%/42.8% (p less than 0.0001); fretfulness, 47.5%/64.7% (p less than 0.0001); vomiting, 4.8%/11.2% (p = 0.0084); anorexia 16.0%/26.3% (p = 0.0001); fever greater than or equal to 38 degrees C, 37.6%/58.5% (p less than) 0.0001); persistent crying, 2.6%/4.5% (p = 0.3557). In addition, infants who experienced a fever greater than or equal to 38 degrees C on the first of two immunizations were more likely to have a temperature greater than or equal to 39 degrees C following the second immunization, 4.2% vs. 12.4% (p = 0.0017). These data strongly support the presumption that children who have had previous reactions following DTP immunization are more likely to have similar reactions upon subsequent immunization.