Third International Standard for Pertussis Vaccine: International confirmation study of activity of British Standard for pertussis vaccine, coded 66/303

The first British Standard (BS) (Code 66/303) for pertussis whole cell vacc ine was prepared from the same suspension of Bordetella pertussis as the no w exhausted Second International Standard for Pertussis Vaccine (2ndIS). Th e BS and the 2ndIS were compared and calibrated in a previous international study. This report describes a small international study, which included t he BS, the 1stIS and the 2ndlS so that the present relationship of these pr eparations to one another could be assessed. The results of this study show that the relationship of the BS to the 1stIS is consistent with Its establ ished unitage of 46 IU per ampoule. The results further show that the poten cy of the BS Is broadly consistent with that of the 2ndIS and that the BS h as not lost activity relative to the 2ndIS (from which it was previously fo und to be indistinguishable). Based on its original calibration and support ed by the results of this present study, the BS has been established as the Third International Standard for Pertussis. Vaccine, with an assigned unit age of 46 IU per ampoule.