Effects of adverse storage on live virus vaccines

A vaccine stored strictly according to the manufacturer's instructions can be used with confidence up to the designated expiry date. However, problems with transport, refrigeration plant, or electricity supply may lead to the exposure of a vaccine under field conditions, and particularly in tropical countries, to high or fluctuating temperatures. We have therefore studied the stability of the standard formulations of our live yellow fever virus, poliovirus and rubella virus vaccines, when they were deliberately exposed to high temperatures, or to alternating cycles of high and low temperatures, intended to simulate such conditions. Our results suggest that with these vaccines, the consequences of adverse storage are not likely to be serious.