In most cases, the term tuberculosis shot refers to the Bacille Calmette Guerin (BCG) vaccine, which is used to combat tuberculosis infection. This vaccine is widely used in countries where tuberculosis infection is common, but is rarely used in the United States. It is generally most successful in the treatment of infected children, and may not be effective against lung-based tubercular infections in adults. The term tuberculosis shot is also sometimes used to refer to the Mantoux skin test. This test is not technically a shot, however, but rather a diagnostic measure used to determine whether an individual is infected with tuberculosis.
The tuberculosis shot known as the BCG vaccine works to stimulate immunity to Mycobacterium tuberculosis, the bacteria which cause tuberculosis. Developed in France in the early 20th century, the vaccine contains a diluted strain of bacteria called Mycobacterium bovis. While these bacteria were derived from cows, they closely resemble the bacteria which cause tuberculosis in humans. As a result, when the vaccine is injected into the human body, it stimulates the immune system to develop resistance against tuberculosis.
While the BCG vaccine is frequently administered in countries where tuberculosis is prevalent — including many parts of Latin America, Asia, Africa, and Eastern Europe — health experts in some nations, such as the United States, advise using it only in special cases. This is primarily because the vaccine does not have high success rates among infected adults. Another concern is that, in rare cases, those with weak immune systems may contract an infection from the BCG vaccine itself. The vaccine is generally considered effective in preventing infection in infants and children, however. Thus, vaccination is important for children in regions where tuberculosis is common as well as those in close contact with an actively infected person.
Occasionally, the term tuberculosis shot is mistakenly used to refer to the Mantoux skin test. This test is not in fact a shot, but rather a diagnostic exam in which a patch of skin on the forearm is pricked with a small amount of a substance extracted from Mycobacterium tuberculosis bacteria. The development of a bump at the site of the skin prick suggests that an individual has preexisting tuberculosis antibodies, which may mean that he is infected with tuberculosis, or may merely show that he received the BCG vaccine in the past. Due to this imprecision, the Mantoux skin test is not a definitive diagnostic tool, but rather a starting point for identifying tuberculosis infection.