Despite extensive immunization with Salk vaccine in Seattle-King County since 1955 and the coincident rapid decrease in poliomyelitis,1 some wariness existed (R.T.R.) concerning the possibility of an outbreak of poliomyelitis among the less-immunized lower socioeconomic groups—such as had occurred in Chicago2 and Detroit.3
An attempt was therefore made during the spring of 1959 to improve the immunization status of the lower socioeconomic groups—by means of additional publicity urging immunization and by making free immunization more readily available. Immunization for poliomyelitis was made more readily available via district clinics and, during June, a door-to-door immunization program was performed in the High Point public housing project in Southwest Seattle which houses 1,200 families and has an annual turnover of 65%.
Subsequently, increasing occurrence of poliomyelitis during June, July, and August, after such preventive measures, caused especial concern—particularly because most of the early cases occurred in and nearby the