Tuberculosis is a disease caused by a ourcobacterium that usually infects the lungs. It can be present in a latent form, where it is not actively harming the body, or in an active form, where the infection is spreading throughout the body. The active form of tuberculosis is contagious to others, but the latent form is not. The latent form of tuberculosis is usually treated with antibiotics in order to decrease the risk of it turning into the active form later in life. The active form of tuberculosis is much more dangerous and more difficult to treat with antibiotics.
The BCG (bacille Calmette-Guérin) vaccine is a live, attenuated vaccine for tuberculosis. It was named after two French scientists, Calmette and Guérin, who developed the vaccine, and is routinely used in countries with a high incidence of tuberculosis. Because of the extremely low incidence of tuberculosis in the United States, the BCG vaccine is not currently recommended in this country, except in very rare circumstances. Specifically, the BCG vaccine is only recommended for children who are continually exposed to adults who have been ineffectively treated for tuberculosis or who have a multidrug-resistant strain of the disease. Alternatively, the vaccine is recommended for healthcare workers who are regularly exposed to multidrug-resistant strains of tuberculosis.
The BCG vaccine is only moderately effective, with an estimated 50 percent protection against active tuberculosis of the lung and up to 80 percent protection against active tuberculosis of other areas of the body. While these protection rates are lower than other vaccines, the disease is so common and so serious in high-risk countries that even that much protection is deemed worthwhile enough to use the vaccine.
The side effects of the BCG vaccine include local skin abscesses and enlarged lymph nodes in 1 to 2 percent of recipients. There are very rare reports of bone infections (osteitis) as well. Because the BCG vaccine contains a live, attenuated virus, it is rarely possible to contract active tuberculosis from the vaccine. About two in every one million vaccine recipients die from active tuberculosis contracted from the vaccine.
Because the vaccine contains a live, attenuated virus, it is not recommended for any person with a deficiency of the immune system. This would include anyone who has HIV or certain kinds of cancer, is receiving chemotherapy or radiation therapy, or has been on medications that suppress the immune system, such as steroids, for more than two weeks. It is also not recommended for anyone who is pregnant or might be getting pregnant due to a theoretical risk to the fetus.
The BCG vaccine is usually only given after consultation with your local or state health department.