Specific immune responses in typhoid fever & after TAB vaccination.

The specific immune responses to Salmonella typhi were investigated in 131 patients suffering from typhoid fever and 34 healthy individuals after TAB vaccination. A proportion of individuals failed to develop either specific humoral or cell mediated immune responses. About 5 per cent of the patients with natural infection and nearly 9 per cent of the vaccine recipients failed to develop both the responses. Frequent reinfection and carrier state, and lack of absolute protection following TAB vaccination could be due to the inability of a proportion of naturally infected and TAB vaccinated individuals to mount sufficient specific immune responses, due to the same mechanism.