The results of a recently completed field trial with a new live oral typhoid fever vaccine show promise that the disease, which is endemic in many parts of the world, eventually may be controlled.
M. H. Wahdan, MD, and colleagues at the High Institute of Public Health, Alexandria, Egypt, the Pasteur Institute, France, and the Swiss Serum and Vaccine Institute, Bern, conducted a controlled trial in Alexandria with 32,388 first-grade schoolchildren. The results of the three-year study were published in the March issue of The Journal of Infectious Diseases.
An attenuated mutant strain of Salmonella typhi was used as the immunogen in the study. Exposure to a high concentration of exogenous galactose (as occurs in the body) causes this strain to lyse within a day or two, but not before its cell wall lipopolysaccharides have provided the necessary antigenic stimuli.
Although a number of S typhi strains exhibit this particular