aP combined vaccines(1) ELISA(1) pertactin(1) EDQM(1) Pertussis toxin(1) biological reference preparation(1) filamentous haemagglutin(1) MIA(1) European Pharmacopoeia(1) Council of Europe(1) fimbriae(1) biological standardisation(1) acellular pertussis(1) collaborative study(1)