The occurrence of diphtheria in medical students and nurses is a significant problem. While the susceptibility rate in this age period is not as high as in children under 10 years of age, the number of susceptibles among individuals 20 years of age and older is sufficiently high to warrant an attempt at immunization, especially since they are exposed frequently to this disease. Toxin-antitoxin has been usually employed in the United States for immunization of students and nurses against diphtheria. The experience with toxin-antitoxin in the immunization of nurses in the Vanderbilt University Hospital has not been satisfactory in that nine out of twenty-four Schick positive nurses receiving from three to four doses of toxin-antitoxin gave a positive reaction approximately six months after receiving the injections, and one of the group developed nasal diphtheria following three doses of toxin-antitoxin.
The effectiveness of this agent has varied in producing immunity. From