Controlled field trials of three different oral killed typhoid vaccines in India.

Three vaccination trials against typhoid fever were carried out in 1968/69, 1970/71 and 1974 in New Dehli. The vaccine was generally administered in tablet form on three consecutive days. Each new trial consisted of a larger number of killed bacteria: 100.10(9), then 300.10(9) and finally 400.10(9) killed S. typhi. The placebo and vaccinated groups were composed of 6,000 to 7,000 persons, sometimes only children from 6 to 17 years. The number of typhoid fever cases which appeared under normal conditions of infection did not show significant difference between the vaccinated and non-vaccinated subjects during the 18 month period of observation.