BCG Vaccine - for prevention of TUBERCULOSIS
Background and General Guidelines
BCG, or bacille Calmette-Guérin, is a vaccine for tuberculosis (TB) disease. BCG is used in many countries, but it is not generally recommended in the United States because of the low risk of infection with M. tuberculosis, the variable effectiveness of the BCG vaccine against pulmonary TB, and the vaccine’s interference with tuberculin reactivity.
BCG vaccines are live vaccines derived from a strain of Mycobacterium bovis that was attenuated by Calmette and Guerin at the Pasteur Institute in Lille, France (29). BCG was first administered to humans in 1921. Many different BCG vaccines are available worldwide. Although all currently used vaccines were derived from the original M. bovis strain, they differ in their characteristics when grown in culture and in their ability to induce an immune response to tuberculin. These variations may be caused by genetic changes that occurred in the bacterial strains during the passage of time and by differences in production techniques. The vaccine currently available for immunization in the United States, the Tice strain, was developed at the University of Illinois (Chicago, Illinois) from a strain originated at the Pasteur Institute. The Food and Drug Administration is considering another vaccine, which is produced by Connaught Laboratories, Inc., for licensure in the United States. This vaccine was transferred from a strain that was maintained at the University of Montreal (Montreal, Canada).
BCG vaccination does appear to lower the risk of serious
complications of primary TB in children. But in the United States, the
consideration of BCG vaccination is recommended only for children who have
negative tuberculin skin test results, and who cannot be given treatment
for latent TB infection but are at high risk for continuous exposure to
infectious TB or to TB that is resistant to isoniazid and rifampin. BCG is
no longer recommended for health care workers or other adults who are
likely to be exposed to TB. However, vaccination of health care workers
should be considered on an individual basis in settings in
Furthermore, BCG should not be given to persons who are immunosuppressed, such as persons who are infected with HIV. It should not be given to pregnant women, even though no harmful effects of BCG vaccination on the fetus have been observed.
In persons vaccinated with BCG, sensitivity to tuberculin is highly variable, depending upon the strain of BCG used and the group vaccinated. The presence or size of a postvaccination tuberculin skin-test reaction does not predict whether BCG will provide any protection against TB disease.
Furthermore, the size of a tuberculin skin-test reaction in a
BCG-vaccinated person is not a factor in determining whether the reaction
is caused by M. tuberculosis infection or the prior BCG
BCG-vaccinated persons who have a positive reaction to the tuberculin skin test, but who do not have TB disease, should be evaluated for treatment of latent TB infection. The possibility of TB disease should be considered for BCG-vaccinated persons who have symptoms suggestive of TB.