Yes, there is a vaccine for tuberculosis, but it works differently than you might expect

The BCG vaccine (Bacille Calmette-Guérin) is the only TB vaccine currently in use worldwide. It has been given to over 4 billion people since the 1920s. But here is the important part: BCG does not prevent TB infection the way a flu shot prevents the flu. Instead, it reduces the chance that someone who gets infected will develop active TB disease, and it is especially effective at preventing severe TB in young children.

In the United States, BCG is rarely given to the general population. Most Americans have never received it. The reason is that TB rates in the U.S. are low enough that the vaccine's modest protection does not outweigh the complications it can cause with certain TB tests. In countries where TB is more common, BCG is part of the standard childhood vaccination schedule.

Key Takeaways

  • BCG is a real vaccine that has been used for a century, but it prevents severe TB disease rather than TB infection itself.
  • The U.S. does not routinely give BCG to children or adults because TB rates are low and the vaccine complicates TB skin testing.
  • BCG is most useful for infants and young children in countries where TB is widespread, where it prevents life-threatening forms of the disease.
  • If you have been exposed to TB, the vaccine does not replace testing and treatment — you will still need a TB test to know your status.
  • Healthcare workers and people with HIV in high-TB settings may be offered BCG, but decisions are made case-by-case based on risk and local guidelines.

How BCG actually protects against TB

BCG is a live, weakened form of the bacterium that causes TB in cattle. When injected, it trains your immune system to recognize and fight TB bacteria. The protection is not perfect — vaccinated people can still get infected with TB — but the vaccine significantly reduces the risk that infection will turn into active disease.

The protection is strongest in children under five. Studies show BCG prevents about 80 percent of severe TB cases (like TB meningitis and disseminated TB) in young children. In older children and adults, the protection against active TB disease is much weaker, ranging from 0 to 80 percent depending on the study and the TB strain in that region. Over time, immunity from BCG fades, which is why a single childhood dose does not protect you for life.

Why the U.S. does not use BCG routinely

The decision not to vaccinate most Americans comes down to risk versus benefit. TB rates in the U.S. are low — about 2.7 cases per 100,000 people per year. At that rate, the small number of TB cases prevented by BCG does not justify vaccinating millions of people, especially because BCG has real drawbacks.

The biggest problem is that BCG interferes with TB skin testing. After you receive BCG, a TB skin test (also called a tuberculin skin test or TST) can show a positive result even if you have never been exposed to TB. This makes it harder to tell who actually has TB infection and who just has immunity from the vaccine. Since the U.S. relies on TB skin testing to find people with latent TB infection, routine BCG vaccination would create confusion in the testing system.

BCG can also cause side effects, though serious ones are rare. The most common is a small scar at the injection site. Severe complications, like BCG disease (when the vaccine bacteria spreads through the body), happen in roughly 1 to 300 per million vaccinated people, usually in those with weakened immune systems.

Who does get BCG in the United States

BCG is not part of the standard U.S. childhood vaccination schedule, but certain groups may be offered it. Healthcare workers with a negative TB test who work in settings with drug-resistant TB may be candidates. People with HIV and a very low CD4 count in areas with high TB rates may also be considered, though this is uncommon.

The decision to give BCG is made on a case-by-case basis by a doctor or TB specialist, weighing the person's individual risk of TB exposure against the vaccine's limitations and side effects. If you think you might be a candidate, talk to your doctor or a TB clinic.

What to do if you have been exposed to TB

If you have been in close contact with someone who has active TB disease, the vaccine is not your next step. You need a TB test instead. The test will show whether you have been infected with TB bacteria. If the test is positive, you may need treatment with TB medications to prevent the infection from becoming active disease.

BCG does not replace testing and treatment. Even if you had received BCG years ago, you still need to be tested after an exposure. Tell the person doing your test that you have received BCG in the past, because they will interpret your skin test result differently.

New TB vaccines in development

Researchers are working on improved TB vaccines that would work better than BCG, especially in adults and in people with HIV. Several candidates are in clinical trials. These new vaccines aim to provide stronger and longer-lasting protection, and some are designed to work alongside BCG rather than replace it. However, none of these are yet available for routine use.

If you are interested in participating in a TB vaccine trial, you can search ClinicalTrials.gov for studies in your area. Participation is voluntary and unpaid trials are common.

Frequently Asked Questions

Can I get BCG if I live in the United States?

Yes, but only if a doctor recommends it for your specific situation. It is not given routinely to children or adults. You would need to see a TB specialist or occupational health doctor who can assess your individual risk and explain the trade-offs.

If I got BCG as a child in another country, do I need TB testing now?

Yes. BCG does not prevent infection, only severe disease. If you have been exposed to TB or live in a setting with TB risk, you should still be tested. Tell the person doing the test that you received BCG, because they will interpret a positive skin test differently.

Does BCG protect me if I travel to a country with high TB rates?

BCG offers some protection, especially against severe TB in children, but it is not reliable enough to be your only defense. The best approach is to avoid prolonged close contact with people who have active TB, and to get tested if you think you have been exposed.

Why does my TB skin test look positive when I have never had TB?

If you received BCG as a child, your skin test may show a positive reaction even though you have not been infected with TB. This is why it is important to tell the person reading your test about your BCG history. They may recommend a blood test (IGRA) instead, which is not affected by the vaccine.

Will a new TB vaccine replace BCG?

Possibly, but not yet. New vaccines in trials show promise, but they are still years away from being available. BCG will likely remain in use in high-TB countries for the foreseeable future, and new vaccines may be added alongside it rather than replacing it entirely.