Study of pertussis vaccines in infants: comparison of response to acellular pertussis DTP vaccines containing 25 micrograms of FHA and either 25 or 8 micrograms of PT with response to whole-cell pertussis DTP vaccine.

Clinical and serological responses of infants to primary vaccination with diphtheria-tetanus-acellular pertussis (DTPa) vaccines containing 25 micrograms of filamentous haemagglutinin (FHA) and either 25 or 8 micrograms of pertussis toxoid (PT) were compared in a double-blind randomized study with responses of infants receiving whole-cell pertussis DTP vaccine (DTPw). In total, 308 healthy infants were enrolled to receive three vaccine doses at 3, 4 and 5 months of age. DTPa recipients had significantly lower incidences of local reactions and fever than the DTPw recipients. No differences in reactogenicity were observed between DTPa groups receiving 8 and 25 micrograms doses of PT. After vaccination, an immune response to PT was seen in 96% of 25 micrograms PT DTPa recipients, 94% of DTPw recipients and 86% of 8 micrograms PT DTPa recipients. The geometric mean anti-PT neutralizing antibody titre was significantly higher for 25 micrograms PT dose recipients (34.9 Chinese hamster ovary (CHO)) as compared with 8 micrograms PT dose recipients (21.0 CHO). The results support the use of the higher dose of PT in acellular pertussis vaccine preparations.