Effect of light on freeze-dried BCG vaccines

Abstract

The effect of light on the viability of freeze-dried BCG vaccine has been studied. The viable counts were carried out on slopes of Lowenstein-Jensen medium. It was found that the viability of all of the freeze-dried BCG vaccines prepared at Connaught Laboratories from the Connaught, French, Danish and Japanese strains was drastically reduced when these vaccines were dispensed in colourless glass vials and exposed to ultraviolet light (366 nm) whereas the viability of these vaccines was effectively protected when dispensed in amber glass vials. The effect of fluorescent light has been investigated only for the BCG vaccine prepared from the Connaught strain. It was found that fluorescent light (3000 μW/cm2) was as damaging to the BCG contained in colourless vials as ultraviolet light (1000 μW/cm2), whereas the protective effect of the amber glass against fluorescent light was of the same order as that observed for the ultraviolet light. Also, all vaccines were equally sensitive to ultraviolet light regardless of the strain employed for their preparation. It is recommended, therefore, that for freeze-dried BCG vaccine the use of colourless glass containers be discontinued, and that containers of lower light transmittance such as amber glass vials be used.