[Effect of diffuse light and heat on 8 BCG vaccines prepared from 4 different strains]

In order to improve our knowledge of the effect of daylight on freeze-dried and rehydrated BCG, 8 BCG vaccines prepared with four BCG strains--Danish 1331, French 1173-P2, English (Glaxo-1077) and Japanese 172--were studied. Four of them were in amber-coloured ampoules manufactured in Copenhagen (K. Bunch -Christensen) and four were in colourless ampoules manufactured by Institut Pasteur Production (Paris). Samples of these vaccines, both freeze-dried and rehydrated for use in children, were exposed to both factors and checked regularly for their viability. Daylight had a deleterious effect on the viability of both freeze-dried and (especially) rehydrated BCG vaccines. The fall in viability began after 2-h exposure of rehydrated vaccines and after 8-h exposure of freeze-dried ones. BCG survival was improved by coloured ampoules. Differences were observed between BCG strains in terms of the light effect, with the French strain being most resistant, the Danish least resistant and the others intermediate. UV irradiation was even more deleterious: 50% survival after 30-min exposure at 20 microW /cm2. In conclusion, since BCG vaccines are sensitive to these factors, they must therefore be protected and their viability checked during BCG vaccination campaigns.