Rabies preexposure prophylaxis with human diploid cell rabies vaccine: a dose-response study.

Recent studies suggest that human diploid cell rabies vaccine (HDCV) may not always produce acceptable titers after intradermal (id) preexposure prophylaxis. To stimulate accidental deviation from the recommended route of administration and to determine the immunogenicity of smaller-than-recommended doses of HDCV, we injected each of 154 persons either intramuscularly (im) with 100%, 10%, or 3% of the standard im dose of vaccine or id with 10%, 3% or 1% of the standard im dose. Seroconversion (titers of antibody greater than or equal to 1:11) was found in all subjects at 49 and 90 days after vaccination. Titers were higher for subjects receiving 100% of the recommended dose im than for those receiving 10% of this dose id (P less than .01); these titers in turn were higher than those from persons receiving smaller doses (P less than .05). Persons receiving 10% or 3% of the standard im dose had lower titers on day 49 than did those receiving the same dose id (P less than .05).