EVALUATION OF TYPHOID VACCINES IN THE LABORATORY AND IN A CONTROLLED FIELD TRIAL IN POLAND. PRELIMINARY REPORT.

In 1961 a controlled field trial of anti-typhoid vaccines was carried out in 25 regions in Poland. Four types of vaccine were studied: (1) bacterial acetone-killed and -dried vaccine (two kinds), (2) bacterial formol-killed phenol-preserved vaccine, (3) Westphal's endotoxin adsorbed on aluminium hydroxide, and (4) Grasset's vaccine (autolysate of typhoid bacilli adsorbed on aluminium hydroxide). The control vaccine was tetanus toxoid. A total of 690 655 persons received two inoculations. Prior to the field trial, laboratory tests were carried out on the vaccines, postvaccinal reactions were studied, and a serological examination was made of randomly selected blood samples. The vaccination was followed by a two-year survey of cases of typhoid and other diseases. Among children aged 5-14 years, the formol-killed phenol-preserved vaccine was found to be the most effective and Grasset's vaccine the least. Among adults aged 15-60 years, no conclusive evidence for the effectiveness of the vaccines could be obtained owing to the small number of cases. This may be due to the maintenance of immunity through repeated annual vaccination with bacterial vaccines.