The purpose of this contract is to conduct a double-blind randomized trial to determine the efficacy of one or more acellular pertussis vaccines. Clinical trials of acellular pertussis vaccines are a top development priority for NIAID and for the PHS. NIAID has been delegated the authority by Congress to conduct efficacy trials in cooperation with the National Vaccine Program Office (NVPO) which has augmented NIAID appropriated funds. A coordinated Phase I/II clinical trial (funded by NIAID) evaluating 13 candidate acellular pertussis vaccines for safety and immunogenicity was completed in June of 1991. The data collected from this trial was used as a basis for recommending seven vaccines to be used in the efficacy trial. Two of the seven vaccines were selected by Sweden to test in field trial to be conducted by the National Bacteriological Laboratory and two acellular vaccines were selected by the Instituto Superiore di Sanita to be tested in a field trial in Italy. The phase III trial, which has been Congressionally mandated, will be performed at a site outside the United States and will address many of the issues that were left unanswered in the efficacy trial performed in Sweden (1987-1989). Sites were developed in Canada, Italy and Sweden following a Part I award September 30, 1990 in response to RFP 90-30. Part II proposals were submitted by the three above mentioned offerors and based on an ad hoc scientific review, the National Bacteriological Laboratory was awarded a contract for the Part II, efficacy trial on September 30, 1991. Since the award of the contract to Sweden, funds have become available to the US government to support a second acellular pertussis efficacy trial. On February 11, 1992, Dalhousie University, Halifax, Nova Scotia officially withdrew their proposal from consideration for funding under RFP 90-30 stating that they had been unable to identify an industry partner to co- fund a pertussis vaccine efficacy trial. The Instituto Superiore di Sanita had identified two manufacturers willing to co-fund a trial in Italy and; therefore, a second award will be awarded. The study will involve one year of recruitment followed by up to two years of surveillance and monitoring for disease. Assuming normal circumstances, data on vaccine efficacy should be available in early 1996. Once safety and efficacy is demonstrated for one or more of these acellular vaccines, licensure for use in infants and children should follow quickly within the United States.