BCGvaccination

The BCG vaccination is a widely used vaccine against tuberculosis. It is typically administered to infants and young children in countries where tuberculosis is common. The vaccine contains a weakened live strain of Mycobacterium bovis, a bacterium closely related to Mycobacterium tuberculosis, the pathogen that causes tuberculosis in humans. The live but weakened bacteria stimulate the immune system to develop a defense against subsequent infection with the actual tuberculosis bacteria.

The effectiveness of the BCG vaccine can vary, with studies showing protection ranging from 0% to 80% against symptomatic tuberculosis. It is generally considered more effective in preventing severe forms of the disease in children, such as tuberculous meningitis and disseminated tuberculosis. The duration of protection is also variable, and booster doses are not routinely recommended in most countries.

BCG vaccination is usually given as a single dose. It is administered intradermally, meaning it is injected into the top layer of the skin, typically on the upper arm. A common side effect is a localized skin reaction at the injection site, which may form a small ulcer and eventually a scar. Other side effects are rare but can include swollen lymph nodes. The BCG vaccine is generally safe and well-tolerated, though contraindications exist, such as severe immunodeficiency. Its widespread use has significantly contributed to the reduction of tuberculosis mortality and morbidity globally, particularly in vulnerable populations.