Controlled field trials of killed oral typhoid and paratyphoid B vaccines and cell-free, chemical aerosol typhoid vaccine.

Three controlled field trials were carried out. One of them (1963) showed that an aerosol with cell-free, chemical typhoid vaccine did not protect vaccinees from the disease. The other trials (1964 and 1965) assessing the efficacy of killed oral typhoid vaccine revealed a short term (up to 3 months) protective effect. In the trial of oral paratyphoid B vaccine no statistically significant difference in morbidity in the test and control groups was observed due to the small number of cases.