September 30 (HealthDay News) -- The anthrax vaccine appears to be just as effective and causes few side effects if given in fewer doses and through intramuscular injection, according to a new study.

The current anthrax vaccine adsorbed (AVA) vaccine is given in six doses -- at zero, two and four weeks then again at six, 12 and 18 months -- below the skin, or subcutaneously, with annual boosters. The study, published in the Oct. 1 issue of JAMA, found intramuscular injection was just as effective at forming antibodies in a three-dose regimen done at zero and four weeks and again at three months.

The study, headed by the U.S. Centers for Disease Control and Prevention in Atlanta, also found the side effects at the injection site -- such as warmth, tenderness, itching, abnormal redness of the skin and swelling -- occurred at lower proportions in those given the shot intramuscularly compared to those receiving it subcutaneously.

"Changing the injection route from SQ (subcutaneously) to IM (intramuscular) may increase vaccine acceptability. Reducing the number of doses in the AVA regimen would have the added benefit of increasing the number of doses available for prophylactic use," the authors concluded.

SOURCE: JAMA, news release, Sept. 30, 2008