A modified vaccine reduces the rate of large injection site reactions to the preschool booster dose of diphtheria-tetanus-acellular pertussis vaccine: results of a randomized, controlled trial.

BACKGROUND

Large injection site reactions commonly follow booster doses of diphtheria-tetanus-acellular pertussis (DTaP) vaccines at 4-6 years of age. A vaccine with lower diphtheria and pertussis dosage (Tdap) might be better tolerated for this dose.

METHODS

We conducted a randomized, controlled, evaluator-blinded comparison of local reactions to DTaP.inactivated poliomyelitis vaccine (IPV) or Tdap booster vaccinations, in 4- to 5.5-year-old children. Reactions were assessed daily by parents and after 48 hours by study nurses. Serologic responses were measured before and 4 weeks after vaccination and examined in relation to large local reactions (>or=50 mm redness and/or swelling).

RESULTS

288 children were vaccinated, 145 with DTaP.IPV and 143 with Tdap, and after 48 hours examiners noted local redness >or= 50mm in 17.2 and 6.3%, respectively (P = 0.004). DTaP.IPV vaccinees initially experienced local pain (in 54%) which limited arm motion (in 37%), but symptoms largely resolved by 48 hours. Tdap vaccinees had fewer symptoms (pain in 20%, limited arm motion in 14%). Children with large reactions to DTaP.IPV more often than nonreactors had elevated preimmunization antibody concentrations to 1 or more of diphtheria, pertussis toxin or pertactin and elevated postimmunization antibody concentrations to all antigens except fimbriae. Booster responses to Tdap were reduced with the smaller antigen doses but were generally satisfactory.

CONCLUSIONS

This preschool DTaP.IPV booster vaccination caused large local reactions in 1 in 5 children, with transient discomfort. With Tdap vaccine, such reactions were significantly fewer but not eliminated. A Tdap.IPV vaccine warrants study for routine use at 4-6 years of age.