Further studies on the heat-stability of freeze-dried glutamate BCG vaccine: Effect of storage at 30 degrees -50 degrees C on allergenic potency in humans.

In order to avoid the necessity for continuous refrigeration of liquid BCG vaccine during storage and transport in hot climates, various attempts have been made to develop more stable preparations. Several studies have indicated that freeze-dried BCG vaccines, and in particular the Japanese glutamate vaccine, are more resistant to high temperatures than liquid BCG vaccines. The present paper reports the results of three studies in schoolchildren designed to compare the heat-stability of three dried vaccines (Japanese glutamate vaccine, Japanese sucrose vaccine, and French glucose vaccine) and Danish liquid vaccine. The results showed that the allergenic potency of the Japanese glutamate vaccine was not much reduced even after storage at 42 degrees C for one month whereas the liquid vaccine was already seriously damaged after one month's storage at 30 degrees C. Exposure to a temperature of 50 degrees C for one month was found to reduce the allergenic capacity of all three freeze-dried vaccines. As exposure to such high temperatures hardly ever occurs under field conditions, it seems probable that the dried glutamate vaccine can be used without refrigeration even in tropical countries. However, the duration of the allergy induced by the heat-treated glutamate vaccine has not yet been definitely established. This question is under further study.