Vaccination is one major preventive measure against TB. A vaccine called BCG (Bacillus Calmette-Guérin, named after its French developers) is made from a weakened mycobacterium that infects cattle. Vaccination with BCG does not prevent infection by M. tuberculosis but it does strengthen the immune system of first-time TB patients. As a result, serious complications are less likely to develop. BCG is used more widely in developing countries than in the United States. The effectiveness of vaccination is still being studied; it is not clear whether the vaccine's effectiveness depends on the population in which it is used or on variations in its formulation.
Prophylactic use of isoniazid
INH can be given for the prevention as well as the treatment of TB. INH is effective when given daily over a period of 6 to 12 months to people in high-risk categories. INH appears to be most beneficial to persons under the age of 25. Because INH carries the risk of side-effects (liver inflammation, nerve damage, changes in mood and behavior), it is important to give it only to persons at special risk.
High-risk groups for whom isoniazid prevention may be justified include:
close contacts of TB patients, including health care workers
newly infected patients whose skin test has turned positive in the past two years
anyone who is HIV-positive with a positive PPD skin test; isoniazid may be given even if the PPD results are negative if there is a risk of exposure to active tuberculosis
intravenous drug users, even if they are negative for HIV
persons with positive PPD results and evidence of old disease on the chest x-ray who have never been treated for TB
patients who have an illness or are taking a drug that can suppress the immune system
persons with positive PPD results who have had intestinal surgery; have diabetes or chronic kidney failure; have any type of cancer; or are more than 10% below their ideal body weight
people from countries with high rates of TB who have positive PPD results
people from low-income groups with positive skin test results
persons with a positive PPD reaction who belong to high-risk ethnic groups (African Americans, Hispanics, Native Americans, Asians, and Pacific Islanders)
David A. Cramer MD, The Gale Group Inc., Gale, Detroit,