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 vaccine was prepared from the same suspension of Bordetella pertussis as the now exhausted Second International Standard for Pertussis Vaccine (2ndIS). The BS and the 2ndIS were compared and calibrated in a previous international study. This report describes a small international study, which included the BS, the 1stIS and the 2ndIS so that the present relationship of these preparations 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 established unitage of 46 IU per ampoule. The results further show that the potency of the BS is broadly consistent with that of the 2ndIS and that the BS has not lost activity relative to the 2ndIS (from which it was previously found to be indistinguishable). Based on its original calibration and supported by the results of this present study, the BS has been established as the Third International Standard for Pertussis Vaccine, with an assigned unitage of 46 IU per ampoule.