Cutaneous responses to tests with influenza vaccines.

Responses to the intracutaneous infection of influenza vaccines were examined at 24 and 48 hours. Whole virus and subunit virus vaccines of comparable potency induced local reactions of comparable magnitude. Cutaneous reactions to the influenza vaccines were present in almost all adults but absent in young children. Reactions were greatly reduced by ingested prednisone. Responses to a subunit commercial trivalent influenza vaccine were compared with responses to tuberculin in tuberculin-sensitive subjects. In each subject the tuberculin reaction had greater duration than the influenza reaction. In separate tuberculin-sensitive individuals the flu vaccine and tuberculin reactions were biopsied at 24 hours. There was mild to moderate cellularity in the responses to both reactants. The cellular infiltration was mainly mononuclear cells except in one case in whom both agents elicited an infiltrate in which neutrophils and eosinophils predominated. The microscopic findings in reactions to tuberculin and influenza vaccine were comparable. Immunofluorescence studies revealed the deposition of complement (C3) in most reactions and of immunoglobulin (particularly IgM) in some reactions of both types. The findings support the view that local reactions to influenza vaccines are acquired and probably immunologic; the difference in duration from tuberculin reactions points to a different pathogenesis which is not yet entirely characterized.