BCG vaccination

BCG vaccination is generally not recommended in the U.S. because of the low risk of infection and the variable effectiveness of BCG vaccine. According to the CDC recommendations were published in 1988, BCG vaccine should only be given to infants and children with negative tuberculin skin test results that are very high risk for tuberculosis. A history of vaccination with BCG does not change the guidelines for the interpretation of tuberculin test in most situations.

Recommendations for use of BCG Vaccine:

BCG, or bacilli Calmette-Guerin, a vaccine against tuberculosis disease, which is used in many countries. However, BCG is not generally recommended in the U.S. because there is little risk of infection with M. tuberculosis and because the effectiveness of BCG has varied widely - from 0% to 76% in eight major studies. In a recent meta-analysis, data from all clinical trials with BCG were collected and analyzed. The protective effect of BCG was found to be 50% against all forms of TB and 64% against TB meningitis. 

There should be caution in applying the results of this meta-analysis of public health practice. Because BCG varies so greatly in effectiveness and because the reason for this difference is unknown, estimates of its effectiveness in different population groups that can not be translated directly to the protective effects in individuals.

Furthermore, BCG vaccination can cause a positive reaction to the tuberculin skin test. Thus it can be difficult to make decisions to provide preventive treatment for BCG-vaccinated individuals who have a positive skin test result.

CDC recommendations for BCG vaccination was most recently was published in November 1988. According to these recommendations, BCG vaccine should be given to infants and children with negative tuberculin skin test results can not be ionized preventive treatment, but will be regularly exposed to someone with infectious TB will be regularly exposed to someone with infectious tuberculosis that are resistant to rifampin and ionized belong to groups where the number of new infections than 1% per year, and for whom the usual surveillance and treatment programs have not been successful (eg, those without access to health care)

These recommendations are currently being revised. Refer to the latest published recommendations.

BCG is contraindicated for persons with impaired immune systems (eg, persons who have HIV infection, leukemia or lymphoma) or who are immunosuppressed because of steroids, alkylating agents, antimetabolites, or radiation. HIV infection should be excluded before the BCG vaccine for persons in groups at high risk for HIV infection. It is also wise to avoid giving BCG vaccination to pregnant women, although no adverse effects of BCG on the fetus have been observed.

Interpretation of tuberculin reactions in persons with previous BCG vaccination. 

Many foreign countries still use BCG as part of their TB control programs, especially for infants. In persons vaccinated with BCG, sensitivity to tuberculin is highly variable, depending on the strain of BCG used and the vaccinated group. There is no reliable method of distinguishing tuberculin reactions caused by BCG from those caused by natural infections.

A response to tuberculin in a person with a history of BCG vaccination is more likely to be due to infection with M. tuberculosis if:

The indurations are large 

The person was vaccinated a long time ago 

The person who is a recent contact with someone with infectious TB 

There is a hereditary TB 

The person who comes from an area where TB is common 

Chest radiograph results show evidence of previous TB 

In a BCG-vaccinated person who has one of the previous risk factors, a positive tuberculin reaction probably indicates infection with M. tuberculosis. Such persons should be evaluated for ionized preventive treatment after the disease has been excluded.