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

A vaccine for tuberculosis exists and has been used worldwide for nearly a century. It's called BCG (Bacille Calmette-Guérin), named after the two French scientists who developed it in the 1920s. But BCG doesn't 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's most effective at preventing the severe forms that kill children.

If you grew up in the United States, you almost certainly did not receive BCG. The U.S. stopped recommending it for most people in the 1980s, even though it remains one of the world's most widely used vaccines. That decision reflects a specific calculation about TB risk in America, not a judgment that the vaccine doesn't work. Understanding why requires knowing what BCG actually does and what it doesn't.

Key Takeaways

  • BCG is a live vaccine that reduces the risk of active TB disease by 60 to 90 percent, depending on the type of TB and the person's age when vaccinated.
  • The vaccine works best in infants and young children, particularly at preventing severe TB meningitis and disseminated TB that can be fatal.
  • The U.S. does not routinely recommend BCG because TB rates are low and the vaccine interferes with tuberculin skin tests used to detect TB infection.
  • BCG is standard in most countries with higher TB rates, where the benefit of preventing severe childhood TB outweighs the drawback of complicating later TB screening.
  • Even vaccinated people can still develop TB if exposed to the bacteria, so BCG is considered one tool among many, not a complete solution.

How BCG protects against TB and its limits

BCG uses a weakened form of the bacterium that causes TB in cattle. When injected, it trains the immune system to recognize and fight TB bacteria, but it does not create perfect immunity. A vaccinated person who is exposed to TB bacteria can still become infected—the vaccine just makes it much less likely that infection will progress to active disease.

The protection varies by age and type of TB. In infants and young children, BCG prevents about 80 to 90 percent of severe TB meningitis (TB that spreads to the brain and spinal cord) and disseminated TB (TB that spreads throughout the body). These are the forms most likely to kill a child. In older children and adults, protection against pulmonary TB (TB of the lungs) is lower, around 50 to 60 percent, and protection wanes over time. By 10 to 15 years after vaccination, immunity may be significantly reduced.

This pattern is why BCG is most valuable in countries where TB is common and children face high risk of exposure early in life. In those settings, vaccinating infants prevents the most dangerous forms of TB before they can occur. In countries where TB is rare, the same benefit is less urgent.

Why the U.S. does not use BCG routinely

The United States has one of the lowest TB rates in the world—roughly 2 to 3 cases per 100,000 people per year. At that rate, the risk that an average American child will be exposed to TB is very small. BCG would prevent some of those rare cases, but it creates a practical problem: the vaccine causes a positive tuberculin skin test (also called a Mantoux test or PPD test).

A tuberculin skin test is the standard way to detect whether someone has been infected with TB bacteria. If someone has been vaccinated with BCG, their skin test will be positive even if they have never encountered TB in real life. This makes it impossible to use the skin test to identify people who are actually infected. In a country with low TB rates, this trade-off is not worth it. The rare cases BCG would prevent are outweighed by the difficulty of screening for TB in vaccinated people.

The U.S. Centers for Disease Control and Prevention (CDC) does recommend BCG for a narrow group: people who will live or work in countries with high TB rates and cannot take preventive TB medications, or healthcare workers in settings where drug-resistant TB is common and infection control is inadequate. But for the general population, the recommendation remains against routine vaccination.

BCG use around the world

BCG is part of the routine childhood vaccination schedule in more than 180 countries. It is given to infants in most of Africa, Asia, Latin America, and Eastern Europe—regions where TB remains a significant cause of childhood death. The World Health Organization lists BCG as an essential vaccine for countries with TB incidence above 1 case per 100,000 people.

Countries with low TB rates but significant immigrant populations sometimes face a different calculation. Canada, for example, does not routinely vaccinate but offers BCG to Indigenous communities and recent immigrants from high-TB countries. Australia recommends it for Aboriginal and Torres Strait Islander infants. These decisions reflect the fact that BCG's value depends partly on local TB risk.

In countries where BCG is standard, healthcare systems have adapted to the challenge of TB screening. They may use blood tests (called interferon-gamma release assays, or IGRAs) instead of skin tests, or they may interpret a positive skin test differently in vaccinated versus unvaccinated people. These alternatives exist but are more expensive and less practical in resource-limited settings.

What happens if you were vaccinated with BCG

If you received BCG as a child—which is likely if you were born outside the U.S., Canada, Australia, or Western Europe—you have some protection against TB, particularly against severe forms. That protection is real but incomplete. You can still develop TB if exposed to the bacteria, especially as you age and immunity wanes.

If you later move to or visit a country with high TB rates, or if you work in healthcare or another high-risk setting, your prior BCG vaccination provides a foundation of protection but does not eliminate the need for other precautions. You should still follow infection control measures, get screened for TB if you have symptoms, and take preventive medications if you are identified as having TB infection.

If you need a tuberculin skin test and have been vaccinated with BCG, tell the healthcare provider. They will interpret the result in that context. A positive test in a vaccinated person does not automatically mean you have TB infection; it may simply reflect the vaccine. An IGRA blood test can help clarify whether you have actual infection.

TB prevention beyond vaccination

BCG is one tool for TB prevention, but it is not the only one. In countries with low TB rates, prevention relies more heavily on early detection and treatment of active TB cases, infection control in healthcare settings, and preventive medications for people who have been exposed to TB or who have TB infection.

If someone has been exposed to TB bacteria but does not yet have active disease, they can take preventive medications—usually isoniazid, rifampin, or a combination—for several months. These medications are highly effective at stopping TB from developing. In high-TB countries, preventive treatment is often reserved for people at highest risk, like children under 5 who have been exposed or people with HIV. In low-TB countries, it is offered more broadly to anyone identified as having TB infection.

Research into improved TB vaccines is ongoing. Several new vaccine candidates are in clinical trials, some designed to boost immunity in people who received BCG years ago, and others intended to replace BCG entirely. These vaccines may offer better protection or work better in older children and adults. None are yet approved for routine use, but they represent the direction TB prevention research is moving.

Frequently Asked Questions

If I was vaccinated with BCG, am I protected for life?

No. BCG protection decreases over time, particularly against pulmonary TB. Studies show that protection against severe TB in young children lasts longest, but protection against TB in older children and adults may decline significantly after 10 to 15 years. This is one reason why BCG is most valuable as an infant vaccine in high-TB countries.

Can I get BCG as an adult if I want it?

BCG is rarely given to adults because it is less effective in older people and because of the skin test problem. If you are an adult planning to work in a high-TB setting and cannot take preventive medications, talk to your doctor about whether BCG makes sense for you. In most cases, preventive medications are preferred.

Does BCG protect against drug-resistant TB?

BCG provides some protection against drug-resistant TB, but the protection is similar to or slightly lower than protection against drug-susceptible TB. It is not a substitute for infection control measures and preventive medications in settings where drug-resistant TB is common.

Why did my skin test turn positive after I got BCG?

BCG causes the immune system to react to TB antigens, so a tuberculin skin test will be positive in vaccinated people. This is expected and does not mean you have TB infection. If you need TB screening, tell your provider you were vaccinated so they can interpret the result correctly or use an alternative test.

Is there a newer TB vaccine being developed?

Yes. Several TB vaccine candidates are in clinical trials, including vaccines designed to boost BCG immunity and entirely new vaccines. Some show promise in early studies, but none are approved for routine use yet. Development of a better TB vaccine remains a priority for global health organizations.