The purpose of this information sheet is to help Indiana residents determine whether and when they should be pre-immunized for rabies. There are no firm state-wide recommendations applicable to everyone. Based on potential exposure and rabies occurrence in the state, each person must determine whether pre-exposure prophylaxis would be beneficial. In addition to the information presented below, consultation with a physician, local health department, and the Indiana State Department of Health might be helpful in reaching an informed decision.

At present, Indiana is considered to have a low level of rabies activity in its wild and domestic animal populations. Over the last 25 years Indiana averaged about 10 rabid bats and 20 rabid skunks each year. However, there have been only 5 rabid skunks found in the state since 1990. The last rabid cat and dog were diagnosed in Indiana in 1984 and 1989, respectively. In spite of the low numbers of rabid animals, all wild carnivores (skunks, raccoons, foxes, and coyotes) and all bats that have exposed a human are considered rabid unless proven otherwise. Rodents and rabbits are almost always considered not rabid. The rabies potential of other species is assessed on an individual basis.

As the raccoon-variant rabies epidemic approaches Indiana from the east, this situation could change dramatically. States which have experienced raccoon-variant rabies have reported an increase in rabid animals, including wild carnivores, domestic animals, and even species that are not usually thought of as rabies candidates such as rabbits and deer. Although the raccoon-variant epidemic is probably at least 2 years away, it is possible that a rabid raccoon could be transported, either intentionally or unintentionally, to Indiana at any time.

Pre-exposure prophylaxis consists of 3 injections of rabies vaccine given intramuscularly or intradermally in the arm. The second injection is given 1 week after the first, and the third injection is given 2 or 3 weeks after the second. The primary purpose of pre-exposure prophylaxis is not to prevent rabies in exposed persons, although some degree of protection against inapparent exposures is afforded by the process. The major benefit of pre-exposure prophylaxis is that when a pre-immunized person is exposed to rabies, complete protection can be achieved with just 2 booster shots 3 days apart. Exposed persons that have not been pre-immunized must receive rabies immune globulin plus 5 injections of vaccine over a period of four weeks. Thus the main benefit of pre-exposure prophylaxis is the rapidity with which immunity develops. Pre-immunized persons must still receive booster shots after every exposure.

Whether to get pre-immunized against rabies depends primarily on a person’s exposure to potentially rabid animals and on the incidence of rabies in those animals. Taken together, these 2 factors determine a person’s risk category. The accompanying chart (Table 1. Rabies Prevention -- United States, 1991: Recommendations of the Immunization Practices Advisory Committee (ACIP), CDC, Atlanta, GA) describes 4 risk categories and the populations that should be pre-immunized. As mentioned above, Indiana currently has a low level of rabies infection in animals (low rabies enzooticity). Thus, veterinarians and their staff, animal control workers, and persons working with wildlife (biologists, trappers, relocators, rehabilitators, etc.) would be considered to be in the "infrequent" category and should be pre-immunized. If and when raccoon-variant rabies reaches Indiana or the state experiences a large outbreak of skunk rabies (high rabies enzooticity), the above named populations would move to the " frequent" category. They would still need to be pre-immunized, but the recommendations for ensuring that an adequate level of immunity is maintained are more rigorous, as explained in a later section. Persons in contact with healthy pets (groomers, trainers, etc.) and those who spend time in wildlife habitat (campers, hunters, etc.) do not need pre-exposure prophylaxis. However, this is an individual decision based on the risk of exposure and also on how much risk a person is willing to accept. No matter what the occurrence of rabies in a geographic area is, it is not recommended that members of the general public be pre-immunized.

The rabies vaccines available in the United States have been used around the world and found to be quite safe. After the 5 dose series, about 25% of vaccinees reported local reactions such as pain, redness, and swelling. About 20% experienced mild systemic reactions such as headache, nausea, abdominal and muscle pain, and dizziness. The occurrence of severe allergic or anaphylactic reactions occurred in less than 1% of vaccinees. There is a slight danger of "immune complex-like" reactions following repeated booster doses.

Individuals can get immunized by their private physician. Groups can receive pre-exposure prophylaxis from a variety of sources: private physicians, certain local health departments and hospitals, etc. The Occupational Health Unit at Methodist Hospital in Indianapolis will, for a reasonable fee, travel to anywhere in the state to vaccinate groups. The vaccine is available to health care providers from medical biologics distributors or from the 3 manufacturers ("Imovax", Pasteur Merieux/Connaught Laboratories, 1-800-822-2463, "RabAvert", Chiron Corporation, 1-800-244-7668, and Smith-Kline, 1-800-366-8900). The cost of pre-exposure prophylaxis depends on the route of administration (intradermal is cheaper) and the health care provider’s markup and administration fees. Typical costs would be approximately $200 to $400 for the 3 dose series. Volume discounts for groups and negotiations with the providers may reduce the expense somewhat.

If you are in the "infrequent" risk category, you are considered to be adequately immunized just by receiving the 3 dose pre-exposure immunization series. If Indiana becomes a high enzootic area, then most pre-immunized persons would move to the "frequent" risk category. In that case, there are 2 options for ensuring adequate protection: boosters every 2 years or antibody titer determination every 2 years. Because there is a very small but real risk of immune complex development after repeated vaccinations, titer determination is the preferred method. Rabies antibody titers can be run at Kansas State University (913/532-5650) and Atlanta Health Associates (800/717-5612). If the titer falls below 1:5, then a booster is indicated. Remember that pre-exposure prophylaxis is not meant to offer complete protection from rabies infection. Two additional injections will still be needed after each exposure for pre-immunized persons.

Physicians, local health departments and the Indiana State Department of Health (317/233-7272) are sources of additional information about risks of exposure and adverse reactions to the vaccine.