Reactions to an Influenza Virus Vaccine in Infants and Children

A RECENT report from this laboratory indicated that maximum antibody response in infants and children is not always achieved with a single injection of influenza virus vaccine.¹In the course of that study reactions to the injected material were noted, and it seemed advisable to report, in some detail, the ill effects encountered. It was readily apparent that the number of reactions was proportional to the amount of virus in the vaccine²and that the severity of the reactions was also related to the virus content. Furthermore, the frequency and severity appeared to be more pronounced than experience with adult groups had demonstrated. These observations, as well as some discussion of dosage of influenza virus vaccines, comprise the bulk of the report. The study was conducted with three groups of approximately 30 children each, whose average age was 3.2 years. The type A PR8 strain of influenza virus