Tuberculosis (TB) is an infectious disease caused by the bacteria , that is transmitted between humans mainly through the air. TB usually affects a person’s lungs (i.e., pulmonary TB) but can also spread to other parts of the body (i.e., extrapulmonary TB). Initial infection with results in a period of latency in the majority (i.e., around 95%) of people, known as latent TB infection. People with latent TB do not have any symptoms, and cannot spread the TB infection to others, however, they can develop active TB disease. Active TB disease occurs when the TB bacteria overwhelm the immune system and begin to multiply, resulting in TB disease, which can occur soon after infection (in approximately 5% of cases) or it can develop long after infection, following a weakening of the immune system. Symptoms of active TB disease include a bad cough, chest pain, fever, and weight loss. People with active TB disease can spread the TB bacteria to others. TB is common in low and middle income countries, however, there are still cases of TB reported in high income countries. Canada has one of the lowest rates of active TB in the world, but new TB cases are still reported in Canada. Canada has had similar annual rates of active TB since the 1980s, and in 2017 the annual rate of active TB in Canada was 4.9 per 100,000 population. Of the 1,796 cases of active TB reported in Canada in 2017, 72% of cases occurred in foreign-born individuals, and 17% of cases occurred in Indigenous peoples born in Canada. These groups with high incidences of TB within an otherwise low TB burden country represent an opportunity for targeted approaches for preventing TB. The Bacillus Calmette-Guérin (BCG) vaccine, is the only vaccine against TB in general use, and it is one of the most widely administered vaccines. Nevertheless, there are still some questions with regards to the effectiveness of the BCG vaccine, particularly, the duration of the effect, and the ability to protect against pulmonary TB in adults. A global registry updated in 2017 indicates that numerous countries still have a universal BCG vaccine strategy (e.g., most of the countries within South America, Africa, and Asia). In Canada, the universal BCG vaccination policy was discontinued in the 1960s and 1970s, with the exception of specific high-risk groups (i.e., selective vaccination). The selective vaccination groups for the BCG vaccine in Canada currently include infants residing in Indigenous communities or other areas with a high annual risk of TB infection (i.e., greater than 0.1% risk); and those working in areas with higher risk of exposure to TB (e.g., health care workers, prison workers, those working with people experiencing homelessness. Other countries that have a selective BCG vaccination strategy include the United States, Australia, Spain, and France. In Greenland, the universal BCG vaccine policy was discontinued in 1990 and reintroduced in 1996. Selective BCG vaccination in high-risk groups in otherwise low TB burden countries may pose challenges such as incomplete coverage of at-risk individuals due to difficulties identifying or reaching these communities. The purpose of this report is to review and critically appraise the evidence pertaining to the effectiveness of the BCG vaccine in populations at risk of exposure to TB, including evidence from high and low TB burden countries. Additionally, evidence-based guidelines with recommendations regarding the use of the BCG vaccine will be reviewed. This information may be used to inform decision making relating to health policy on the use of the BCG vaccine. This report is a component of a larger CADTH Condition Level Review on TB. A condition level review is an assessment that incorporates all aspects of a condition, from prevention, detection, treatment, and management. For more information on CADTH’s Condition Level Review of TB, please visit the project page (https://www.cadth.ca/tuberculosis).