This article is only available in the PDF format. Download the PDF to view the article, as well as its associated figures and tables. GENERAL PLAN OF THE IMMUNIZATION PROGRAM In March 1942 the Boston Health Department instituted a pertussis immunization program in an effort to protect children against pertussis during the earlier months of their lives. All presumably susceptible infants between the ages of 6 and 12 months were eligible to receive prophylactic inoculations against pertussis at their local well baby clinic. The well baby clinics are located in the health units and substations situated in eighteen different geographic districts of the city and are accessible to all who wish to take advantage of their services. Two different antigens, the Parke Davis Sauer vaccine and the Lederle Detoxified Pertussis Antigen, were used for immunization. The former is a killed bacterial suspension of phase I Hemophilus pertussis cultures grown on Bordet-Gengou medium containing at least 15 per cent of human (placental) blood made up to a concentration of 15 billion