An open study evaluating the reactogenicity and immunogenicity of a DTP vaccine containing an acellular pertussis component in four to six year old children.

Acellular pertussis vaccines have been used for mass immunization of children in Japan since the fall of 1981, but until recently they have not been evaluated in the United States. We report a trial with a DTP vaccine containing an acellular pertussis component in 36 four to six year old children who had previously received four doses of United States DTP licensed vaccine with a whole cell pertussis vaccine component. The study vaccine contained diphtheria and tetanus toxoids and 300 HA units of Takeda acellular pertussis component. The principle immunizing antigens in the pertussis component of the vaccine were lymphocytosis promoting factor (LPF) and filamentous hemagglutinin (FHA). Local and systemic reactions were monitored during the first 48 hours after vaccination, and pre-immunization and one month post-immunization serum specimens were obtained for antibody assay. The following reaction rates were noted: redness 50%, tenderness 50%, swelling 41%, fever (greater than or equal to 38 degrees C) 3%, drowsiness 17%, fretfulness 14%, anorexia 11%, and vomiting 6%. Pertussis antibody values (preimmunization/postimmunization) were as follows: agglutinin GMT, 1:21/1:100; FHA mean ELISA u, 28 +/- 6/greater than or equal to 229 +/- 47; LPF mean ELISA u, 176 +/- 59/1732 +/- 280. The pertussis component of the study vaccine would appear to be less reactogenic than United States whole cell pertussis vaccines but still immunogenic when given as a booster immunization to four to six year old children. Further studies are needed to assess reactions and immunogenicity in younger and previously unimmunized children.