INTERNATIONAL REFERENCE PREPARATIONS OF TYPHOID VACCINE. A REPORT ON INTERNATIONAL COLLABORATIVE LABORATORY STUDIES.

Before their establishment as International Reference Preparations of Typhoid Vaccine, an acetone-inactivated vaccine (vaccine K) and a heat-phenol-inactivated vaccine (vaccine L) were tested on man in large-scale controlled field trials and simultaneously subjected to extensive collaborative laboratory studies on their relative potencies. Some 20 laboratories in 12 countries took part in these collaborative studies. This paper describes in detail the results of the investigation of 14 different assay procedures.One of the main objects of these studies was to determine whether one or more of the laboratory methods showed a correlation with the protective effectiveness of the vaccines against typhoid fever in man. It is clear from the results reported that none of the potency tests in animals reliably reflected the evidence obtained in human beings in the controlled field trials. Some of the assays, however, seem to offer promise of ability to distinguish between the potencies of typhoid vaccines in a manner reflecting their efficacy in man. Further research is needed before the value of these procedures can be definitely assessed.