We compared immunogenicity and reactogenicity of a single dose of DTaP vaccine (containing tetanus and diphtheria toxoids and four acellular pertussis antigens) with conventional Td- or d-vaccines in 180 German adults. Antibody values against diphtheria and tetanus toxin and against the pertussis antigens fimbriae (FIM), filamentous hemagglutinin (FHA) and pertussis toxin (PT) were measured in pre- and post-immunization sera. Reactogenicity was determined by a patient diary card. Pre-immunization antibody values against diphtheria toxin were low in all three vaccine groups. After immunization, > or = 80% of the vaccinees in all three groups were fully protected (> or = 0.1 IU/ml), but geometric mean values were significantly higher in DTaP recipients compared to Td or d recipients (1.65 vs. 0.44 and 0.48, respectively; both P < 0.05). Pre-immunization antibody values against tetanus toxin were high in all three groups, and after immunization 100% of the vaccinees were protected (> or = 0.1 IU/ml). Furthermore, substantial antibody responses against pertussis antigens were elicited in DTaP recipients with geometric mean rises of 22.5, 4.1 and 7.5 for antibodies against FHA, fimbriae and PT, respectively. All three vaccines were well tolerated. Frequency and severity of local reactions were similar between DTaP and Td recipients and even less common in d recipients. Since DTaP did provide a significant boost of anti-pertussis antibodies and a significantly higher anti-diphtheria response than conventional Td vaccine without an increase of side effects, it might be an appropriate candidate for use in adults.