BCG, or bacille Calmette-Guérin, is a vaccine for
tuberculosis (TB) disease. Many foreign-born persons have been BCG-vaccinated.
BCG is used in many countries with a high prevalence of TB to
prevent childhood tuberculous meningitis and miliary disease.
However, BCG is not generally recommended for use in the United
States because of the low risk of infection with Mycobacterium
tuberculosis, the variable effectiveness of the vaccine against
adult pulmonary TB, and the vaccine’s potential interference with
tuberculin skin test reactivity. The BCG vaccine should be
considered only for very select persons who meet specific criteria
and in consultation with a TB expert.
Children. BCG vaccination should only
be considered for children who have a negative tuberculin skin test
and who are continually exposed, and cannot be separated from,
- Are untreated or ineffectively treated for TB disease (if the
child cannot be given long-term treatment for infection); or
- Have TB caused by strains resistant to isoniazid and rifampin.
Health Care Workers. BCG vaccination of
health care workers should be considered on an individual basis in
settings in which
- A high percentage of TB patients are infected with M. tuberculosis strains resistant to both isoniazid and rifampin;
- There is ongoing transmission of such drug-resistant M.
tuberculosis strains to health care workers and subsequent
infection is likely; or
- Comprehensive TB infection-control precautions have been
implemented, but have not been successful.
Health care workers considered for BCG
vaccination should be counseled regarding the risks and benefits
associated with both BCG vaccination and treatment of latent TB
Immunosuppression. BCG vaccination should not be given to
persons who are immunosuppressed (e.g., persons who are HIV
infected) or who are likely to become immunocompromised (e.g.,
persons who are candidates for organ transplant).
Pregnancy. BCG vaccination should not be given during pregnancy.
Even though no harmful effects of BCG vaccination on the fetus have
been observed, further studies are needed to prove its safety.
Testing for TB in BCG-Vaccinated Persons
The tuberculin skin test (TST) and blood tests to detect TB
infection are not contraindicated for persons who have been
vaccinated with BCG.
Tuberculin Skin Test (TST). BCG vaccination may cause a
false-positive reaction to the TST, which may complicate decisions
about prescribing treatment. The presence or size of a TST reaction
in persons who have been vaccinated with BCG does not predict
whether BCG will provide any protection against TB disease.
Furthermore, the size of a TST reaction in a BCG-vaccinated person
is not a factor in determining whether the reaction is caused by
LTBI or the prior BCG vaccination. (See below for specific guidance
on skin test results.)
TB Blood Tests. Blood tests to detect TB infection, unlike the
TST, are not affected by prior BCG vaccination and are less likely
to give a false-positive result.
Treatment for LTBI in BCG-Vaccinated Persons
Treatment of LTBI substantially reduces the risk that TB
infection will progress to disease. Careful assessment to rule out
the possibility of TB disease is necessary before treatment for LTBI
is started. Evaluation of TST reactions in persons vaccinated with
BCG should be interpreted using the same criteria for those not BCG-vaccinated.
Persons in the following high-risk groups should be given treatment
for LTBI if their reaction to the TST is at least 5 mm of induration
or they have a positive result using a TB blood test:
- HIV-infected persons
- Recent contacts to a TB case
- Persons with fibrotic changes on chest radiograph consistent
with old TB
- Patients with organ transplants
- Persons who are immunosuppressed for other reasons (e.g., taking
the equivalent of >15 mg/day of prednisone for 1 month or longer,
taking TNF-a antagonists)
In addition, persons in the following high-risk groups should be
considered for treatment of LTBI if their reaction to the TST is at
least 10 mm of induration or they have a positive result using a TB
- Recent arrivals (less than 5 years) from high-prevalence countries
- Injection drug users
- Residents and employees of high-risk congregate settings (e.g.,
correctional facilities, nursing homes, homeless shelters, hospitals,
and other health care facilities)
- Mycobacteriology laboratory personnel
- Persons with clinical conditions that place them at high-risk
for developing TB disease (e.g., diabetes)
- Children less than 4 years of age, or children and
adolescents exposed to adults in high-risk categories
Persons with no known risk factors for TB may be considered for
treatment of LTBI if their reaction to the tuberculin test is at
least 15 mm of induration or they have a positive result using a TB
blood test. Targeted skin testing programs should only be conducted
among high-risk groups. All testing activities should be accompanied
by a plan for follow-up care for persons with TB infection or
Last Modified: 11/19/2008
Last Reviewed: 05/18/2008
Content Source: Division of Tuberculosis Elimination
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention