RESULTS OF THE STUDY OF TYPHOID VACCINES IN FOUR CONTROLLED FIELD TRIALS IN THE USSR.

In field trials of typhoid vaccine in the USSR, a comparison was made of the effectiveness of chemical, heat-killed, and alcoholized vaccines. All of them conferred protection if administered in sufficient dosage, and variations in effectiveness could usually be traced to size of dosage. The heat-killed vaccine, however, appeared to be significantly more effective than the others. The immunological history of a vaccinated person apparently had no essential influence on the effectiveness of a vaccine, and the data indicated that two doses of the vaccine conferred no greater protection than one.