Evaluation and control of vaccines for the National Influenza Immunization Program

The National Influenza Immunization Program of 1976 offered an ideal opportunity to test the capability of the system in the United States for production and distribution of maximal amounts of inactivated influenza virus vaccine of carefully regulated quality. The four licensed manufacturers were able to produce and distribute greater than 10 million doses of vaccine per week over a 14-week period. Assays showed that the quality of these vaccines was comparable to or exceeded that of vaccines produced in recent years under less stressful circumstances. Because of the extensive clinical trials conducted as part of the program, it was possible to make an unprecedented evaluation of the significance of various laboratory tests of vaccines in relation to their pertinence in prediction of immunogenicity and reactivity for humans. This experience demonstrated the superiority of immunodiffusion methods as compared with the standard chick cell-agglutination method for assay of vaccine potency. Qualitative differences in immunogenicity between whole-virus and disrupted-virus vaccines were recognized that are not measured by in vitro potency tests. The results also indicated that influenza viral components are responsible for most febrile reactions to the vaccine.