We examined the antibody response to a rabies vaccine doubly inactivated with 0.025% beta-propiolactone and 0.1% tri(n)butyl phosphate and stabilized with 2.5% human serum albumin. Antibodies were measured by using the following four antigen preparations: complete doubly inactivated rabies vaccine, rabies vaccine inactivated only with tri(n)butyl phosphate, beta-propiolactone and human serum albumin, and human serum albumin alone. The fluid phase of the preparation of beta-propiolactone and human serum albumin completely inhibited IgE binding to solid-phase vaccine. Of 21 subjects with urticarial reactions to a booster, 19 had IgE to doubly inactivated vaccine and to beta-propiolactone and human serum albumin. None of 27 immunized subjects without urticaria had detectable IgE. In paired pre- and postimmunization sera, IgE appeared in six of seven of the subjects with urticaria and in one of seven nonreactors. These sera did not contain a significant level of IgE to singly inactivated vaccine or to human serum albumin alone.

A human diploid cell strain vaccine (HDCV) was evaluated in 90 persons treated after exposure to rabies, 21 of whom were bitten by proven rabid animals. Intramuscular doses of HDCV were given on days 0, 3, 7, 14, and 28, and human rabies immune globulin (HRIG) was given on day 0. Antibody to rabies virus was tested for by the rapid fluorescent focus inhibition test; adverse reactions were assessed from physician's forms. All 87 persons tested developed titers of greater than or equal to 0.5 international units (IU)/ml, with a maximum geometric mean titer of 15.0 IU/ml on day 42. One year after vaccination, all 33 persons tested had antibody to rabies virus. After one or more doses of vaccine, mild local or systemic reactions were reported in 19.0% and 21.4% of persons, respectively. No serious reactions occurred. The results show that this HDCV (plus HRIG) was safe and effective in eliciting antibody in postexposure prophylaxis of rabies. When it becomes available, it is recommended over the present treatment regimen.