A new human rabies vaccine, RabAvert, is prepared from purified chick embryo cell culture (PCEC) and marketed for pre- and post-exposure prophylaxis against rabies infection. Although rabies is rare in the United States, thousands of persons receive postexposure prophylaxis each year. All rabies vaccines for human use are prepared in cell culture and are much safer than the rabies vaccine prepared from infected animal brains, which is used in some countries. The widely used HDCV vaccine is associated with a 6 percent incidence of serum-sickness–like (type III) hypersensitivity reactions to booster doses given months or years after the primary series. Consultants for the Medical Letter reviewed the procedure for pre- and postex-posure prophylaxis of rabies infection.
The wounds of patients exposed to rabies should be thoroughly washed, and human rabies immune globulin should be given in a dosage of 20 IU per kg. As much of the dose as possible should be infiltrated at the site of the wound, with the remainder given intramuscularly at a site distant from the vaccine injection. At the same time, a 1-mL dose of rabies vaccine (HDCV, RVA or PCEC) should be given intramuscularly in the deltoid (or the anterolateral thigh in children) and repeated on days 3, 7, 14 and 28 after the initial dose. Persons previously immunized with a cell-culture vaccine or those who have had a documented antibody response to other rabies vaccine do not need to receive rabies immune globulin and should be given only two doses of rabies vaccine, on day zero and day 3. The PCEC vaccine has been shown to be 100 percent effective in preventing rabies in patients with high-risk exposures.
Persons at high risk, such as veterinarians, animal control workers, wildlife professionals, people working with the rabies virus and travelers visiting rabies-endemic areas, should receive three 1-mL injections of rabies vaccine intramuscularly in the deltoid on days zero, 7 and either 21 or 28. Only the HDCV vaccine has been shown to be effective in a dosage of 0.1 mL when given intradermally. Persons with risk of frequent rabies exposure should have their antibody titers checked or receive a booster dose every two years.
Changing from one rabies vaccine to another during a pre- or postexposure series is not recommended because effectiveness data is lacking. Use of PCEC as a booster has been shown to produce a marked anamnestic response in antibody titers when HDCV was used as the primary vaccination. Certain medications, including antimalarial agents, corticosteroids and other immunosuppressive drugs, may interfere with antibody response to rabies vaccine.
Mild erythema, swelling and pain may occur at the site of injection of the PCEC vaccine. Serum-sickness hypersensitivity reactions like those associated with booster doses of HDCV have not been reported with PCEC. Although rare, anaphylaxis and severe neurologic symptoms have been reported temporally with PCEC. Persons with severe egg allergy should not be given the PCEC vaccine.
Medical Letter consultants report that the new rabies vaccine appears to be as effective as previously available rabies vaccines. Unlike the other vaccines, however, it does not appear to cause the serum-sickness–like hypersensitivity reactions associated with booster doses of the HDCV vaccine.