Studies on pertussis immunization

Abstract

Summary Contrary to popular opinion, young infants are able to produce antibodies as a result of pertussis immunization just as well as older children. In the immunization of these young infants, prolonged antigenic stimulus as afforded by alum precipitation is necessary for efficient antibody production. The alumprecipitated vaccine, except for its tendency to produce sterile abscesses, gave far less local and systemic reactions than the fluid or combined vaccines. Severe reactions were an infrequent occurrence with the young infants. Local and systemic reactions were associated with high agglutinin titers indicating that, although undesirable from the practical standpoint, they are highly desirable immunologically. Following pertussis immunization the agglutinins reach a plateau level in two to four months and remain at this level practically unchanged for at least three years. A “stimulating dose” of pertussis vaccine administered eight to twelve months following completion of immunization of young infants raises the agglutinin titer to higher levels within one month, after which the plateau is maintained for two years or longer. A follow-up of immunized and nonimmunized children with known agglutinin titers shows that immunization of young infants below 3 months of age is highly effective and supports the contention that, although immunity may exist in the absence of agglutinins, susceptibility does not occur in the presence of agglutinins in high titers (1:320 or above).