The efficacy of six acellular pertussis vaccines, prepared by various manufacturers in Japan, was investigated in a murine model of respiratory infection (aerosol challenge model) and a murine intracerebral (i.c.) challenge model. There was a good correlation between bacterial clearance from the lungs after aerosol challenge and the potency of vaccines as determined by i.c. challenge. The levels of antibodies against filamentous hemagglutinin were higher after immunizations with all tested vaccines than the levels of antibodies against pertussis toxin and pertactin. Spleen cells from mice immunized with each individual vaccine secreted interferon gamma (IFN-gamma) in response to stimulation by pertussis toxin, filamentous hemagglutinin and fimbriae. The production of interleukin-4 in response to each of the antigens tested was detected but was lower than that of IFN-gamma. However, antibody levels and cell-mediated immune responses were not correlated with the protective effects of the vaccines after aerosol challenge and after i.c. challenge.