Effectiveness of oral killed typhoid vaccine.

A controlled field trial of oral killed typhoid vaccine was carried out in Delhi, India in 1968-69. Altogether, 13 374 children below the age of 17 years were included in the study. Two comparable groups of children were given either placebo or vaccine. Each tablet of vaccine contained 100x10(9) killed Salmonella typhi, and 3 tablets of vaccine or placebo were administered to each child. The vaccinated subjects were followed up from 10 June 1968 to 31 August 1969. The effectiveness of the vaccine was measured by comparing the incidence of typhoid fever (based only on bacteriologically positive cases) in the two groups. It was found that the difference in incidence of the disease in the two groups was not statistically significant. The oral killed typhoid vaccine in the dosage schedule used in the present trial was found not to be effective against the disease.