CO-OPERATIVE STUDIES OF METHODS FOR ASSAY OF BCG VACCINE. WORLD HEALTH ORGANIZATION

Co-operative studies-co-ordinated by the WHO Tuberculosis Research Office, Copenhagen- of methods for the assay of BCG vaccine were undertaken in 1959 by eight laboratories in seven countries. All the laboratories received the same four vaccines; seven of them carried out viability counts by formally standardized techniques and one made estimations of the total number of bacilli per millilitre by its own technique. In addition, some laboratories assayed the vaccines by special methods, such as examination of germination capacity, distribution of clumping, and uptake of (14)C-labelled acetate, mouse-protection tests and tests of the ability of the bacilli to multiply in mice.The data obtained are presented here in full, together with a detailed statistical analysis. The results are not immediately encouraging: the viability counts for the same vaccines differed distinctly from laboratory to laboratory and the variability of the individual counts within the same laboratory was mostly much larger than would have been expected theoretically. However, it appears that the relatively sophisticated statistical methods used, if applied to routine laboratory findings, might be of considerable value in pin-pointing the most significant sources of experimental error in a given laboratory. It is also felt that this extensive collection of data may be useful as a reference source whenever a particular aspect of BCG standardization is in question.