Diphtheria Immunity Status in Montgomery County School Seniors and Adults

Abstract

IPPHTHERIA, onice primarily a disease of infants and young children, has been increasing among adults and teen-aged children over the past 20 years (1-4). The shift in age-specific morbidity rates can be traced to markedly decreasing exposures to virulent Corynebacterium. diphtheriae. The almost universal artificial immunization of infants and children has resulted in less frequent natural immunity among adults. Somewhere between the adult and the child, lhowever, lies a zone where the protection of unreinforced early immunization begins to wear off. Outbreaks of diphtheria in Detroit, Mich., Albuquerque, N. Mex., and South Carolina in the fall of 1956, while this study was still in the planning stages, pointed up the importance of continued awareness of the disease as a public health problein (5, 6). It also reemphasized the value of current data on the relative immunity of various population segments in anticipating and preventing outbreaks. In this study we undertook specifically to determine the relative immunity to diphtheria of the young adult population in an area where only 2 cases, both in white men in their early twenties, have been reported during the preceding 2 years. The study was conducted in Montgomery County, Md., during January and February 1957. The county, principally a suburban residential center, is northwest of the District of Columbia and has an area of about 525 square miles. Its population, growing at a prodigious rate in the postwar period wvith the influx of Governament workers, is niearly 300,000. Of these, 6 percent are Negro. The county has the highest per capita income in Maryland. Information gathered at the time of preschool conferences over the past 4 years reveals that about 92.5 percent of Montgomery County children have been actively immunized against diphtheria prior to registering for school, and the remainder are almost all given prinmary immunizations at this time (7). However, because of the large population influx, the inadequacy of transferred school health records, and basic doubt as to the duration of immunization in infancy and early childhood (8), the status of children finishing high school has been heretofore unknown. With the approval of the Montgomery County Medical Society and the superintendent of schools and the aid of the Maryland State Departmenlt of Health, the Montgomery County Health Department planned to give Schick tests to all 12th grade students in the county's nine high schools.