SEROLOGICAL RESPONSES OF MAN TO TYPHOID VACCINES.

Study of the serological responses in man to typhoid vaccines tested in several WHO-sponsored controlled field trials in British Guiana, Poland and Yugoslavia has not indicated any correlation between the level of Vi and O antibodies elicited and the effectiveness of the vaccines. Instead, the more effective vaccines have elicited significantly greater H-antibody responses; but a variety of factors suggests that it may in fact not be the antibody that confers immunity to the disease. The phagocytic test does not appear promising as a technique for determining the effectiveness of a typhoid vaccine, but passive protection of the chick-embryo may warrant further investigation.