Decision-based evaluation of recommendations for preexposure rabies vaccination.

P reexposure rabies vaccination is recommended for individuals who are more likely to be exposed to rabies virus than the general public. 1 This vaccination series consists of 3 doses of vaccine administered IM or intradermally (ID), which permits postexposure vaccination to consist of 3 doses of vaccine rather than 5 and eliminates the need for postexposure administration of human rabies immune globulin. Preexposure vaccination may provide protection for persons with unrecognized exposures and those encountering a delay in receiving postexposure vaccination. 1 Presently, 3 vaccines are approved for use in the United States; only the human diploid cell vaccine (HDCV) is prepackaged and approved for IM and ID use. 2,3 The rabies vaccine, adsorbed (RVA) was approved by the FDA in 1988, and the rabies vaccine, purified chicken embryo cell (PCEC) was approved by the FDA in 1997; both are approved for IM use only. 4,5 Vaccination by the ID and IM routes induces seroconversion in nearly 100% of healthy individuals. 6 Successful seroconversion is defined by the Centers for Disease Control and Prevention (CDC) as virus neutralizing antibody (VNA) ≥ 1:5 serum dilution as determined by the rapid fluorescent focus inhibition test (RFFIT). 1 Differences between the ID and IM routes of administration include cost and longevity of the measurable immune response. Intradermally administered vaccines are approximately half the cost of IM administered vaccines but can have a shorter duration of measurable immune response, necessitating more frequent booster doses. 7 Adverse reactions to vaccination range from mild local reactions such as pain at the injection site to more severe systemic type-III hyper-sensitivity (immune complex mediated) reactions such as serum sickness. 8-10 There have also been infrequent reports of a neurologic syndrome (Guillain-Barre) associated with booster doses of rabies vaccine. 11 Recommendations set forth by the Advisory Committee on Immunization Practices (ACIP) for preexposure prophylaxis and maintenance of a detectable antibody titer differ depending on the estimated degree of risk of exposure to the rabies virus. 1 Four risk categories (continuous, frequent, infrequent, and rare) have been established, and classification depends on factors such as the occupation of the individual and geography (Appendix). 1 To maintain measurable immunity in individuals in the frequent risk group, the 1991 ACIP guidelines recommended that they receive a booster dose every 2 years or have sero-logic testing performed, with booster doses to be administered only when antibody concentrations were below an acceptable value. …