Reactogenicity and immunogenicity of parenteral monovalent influenza A/Victoria/3/75 (H3N2) virus vaccine in healthy adults.

Monovalent influenza A/Victoria/3/75 whole-virus vaccines prepared by Merck Sharp and Dohme (West Point, Pa.) and Merrell-National Laboratories (Cincinnati, Ohio) and split-virus vaccines prepared by Parke, Davis and Company (Detroit, Mich.) and Wyeth Laboratories (Philadelphia, Pa.) containing 200, 400, and 800 chick cell-agglutinating units per dose were compared with a placebo in double-blind trials in which 208 adults participated. Titers of hemagglutination-inhibiting antibody of greater than or equal to 1:20 were found in greater than 80% of the volunteers 21 days after vaccination. Seroconversion, defined as a fourfold or greater increase in antibody titer, occurred more frequently among seronegative volunteers than among seropositive volunteers. The geometric mean titers obtained with the whole-virus or split-virus vaccines were not significantly different. Reaction rates had no relation to seroconversion, nor did seronegative subjects have more reactions than seropositive subjects. Local reactions from all vaccines increased with increasing dose. Significantly more overall reactions, "bothersome" reactions, and febrile reactions occurred in the recipients of whole-virus vaccine. Of nine volunteers who reported temperatures of greater than 100 F, one had received split-virus vaccine, seven had received whole-virus vaccine, and one had received the placebo. Most systemic reactions were mild, and all were self-limited.