In 1934, soon afterthe paper entitled "Immunization with Bacillus Pertussis Vaccine" was published inThe Journal,1Dr. John W. H. Pollard, Evanston2Commissioner of Health, opened a municipal whooping cough prophylactic vaccination clinic at the "Health Center." Diphtheria had been rendered an infrequent disease, 133 cases with ten deaths in ten years. Whooping cough was twenty-five times more prevalent, 3,338 cases with five deaths. Because immunization with diphtheria toxoid had been reported less permanent when given in very early life, and as most deaths from pertussis occur during infancy, pertussis vaccination is given before diphtheria toxoid—preferably between seven and ten months. At least several months intervene between pertussis vaccination and any other immunization procedure. To determine whether the customary total dosage of 8 cc. of authorized commercial vaccine is sufficient to protect children more than 2 years old, fifty "Welfare" children between 2 and 4 years of age