Abstract
The prophylaxis of typhoid fever in Romania is usually achieved with fluid heat-killed phenolized vaccine. However the shelf life of this vaccine is only two years. The long term storage of an intradermal typhoid vaccine is made possible by lyophilization. A heat-inactivated bacterial suspension with a high concentration of organisms, at least 25 × 109 cells per ml, was freeze-dried at a temperature not higher than 30°C. The final vaccine obtained had a residual moisture content of not more than 5%.Active and passive protection tests in mice, specific agglutinin production in humans and rabbits, the innocuity and the toxicity for mice, and the investigation of post-vaccinal adverse reactions in man, showed that the lyophilized typhoid vaccine could be stored at 4°C for at least five years without loss of potency. Consequently, the vaccine may be stored without risk of deterioration for rapid emergency mass immunization with Jet-injector apparatus.
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