BCG Vaccine for Tuberculosis

The BCG vaccine, short for Bacille Calmette-Guerin, is a vaccine against tuberculosis disease. Many people born outside the United States received it as babies. It is given to infants and small children in countries where TB is common¹. It was first given to people in 1921, CDC reported in 1996⁴. The germ it is made from had been weakened at the Pasteur Institute⁴. Several BCG strains are made, and the Danish strain is the most used worldwide despite a global manufacturing interruption in 2015⁷.

The small scar it can leave on the arm is how many people know they had it. A BCG vaccine scar is usually a small round mark on the upper arm.

Yes: the BCG vaccine is a vaccine for tuberculosis. It prevents deaths from TB and protects children from serious forms of the disease, as WHO stated in 2026. The US-licensed BCG vaccine label lists the prevention of TB in people not previously infected with TB germs⁵. The same label says it may not protect everyone who gets it⁵. An experimental vaccine, M72/AS01E, gave 49.7% protection against lung TB over 3 years (Tait, 2019). The adults in the trial were aged 18 to 50 and already had TB infection. That trial enrolled 3,575 adults in Kenya, South Africa and Zambia and reported its final results in 2019. Testing and treating inactive TB, also called latent TB infection, is the main path to TB prevention in the US¹.

The BCG vaccine is not generally used in the United States because TB infection risk is low and its protection varies. It can cause false-positive skin tests too, the third of the reasons CDC gave in 2025. In provisional CDC data released in 2026, the US reported 10,260 TB cases in 2025, a rate of 3.0 per 100,000³. Across case-control studies since 1975, BCG efficacy ranged from zero to 80%, as CDC reported in 1996⁴. That low count of tuberculosis cases in the US is the first of the three reasons.

The BCG vaccine is given to babies and small children in countries where TB is common. In the US it is considered only for a child who lives with an adult whose TB is untreated or resistant. That child must have a negative TB test and be unable to be separated from that contagious adult¹. Some health care workers may be considered where drug-resistant TB is common and infection control has failed¹. A TB expert is always involved. Resistant here means TB germs resistant to both isoniazid and rifampin, as CDC defined in 2025¹. Most US care for tuberculosis treatment in children relies on testing and treatment, not the vaccine.

The BCG vaccine protects children against severe forms of active TB disease. Those forms include TB meningitis, which affects the brain, and miliary TB, which spreads through the body. Its effect against lung TB in adults is variable¹. An estimated 100.5 million BCG doses were given to infants in 2002 (Trunz, 2006). They prevented about 29,729 cases of TB meningitis in the first 5 years of life. That is about one case prevented per 3,435 vaccinations. The same doses prevented an estimated 11,486 cases of miliary TB. Most of the benefit fell in South East Asia (46%) and sub-Saharan Africa (27%). The authors judged BCG highly cost-effective against tuberculous meningitis and said it should be kept where TB is common.

The BCG vaccine works best against severe TB in young children and less reliably against lung TB in adults. A 2014 review of randomized trials found the strongest protection in infants and in children tested before vaccination. Against lung TB, vaccinated infants had a rate ratio of 0.41, and children skin tested first had 0.26 (Mangtani, 2014). A ratio below 1 means fewer cases among the vaccinated. In children not strictly tested first, protection was weaker, with a rate ratio of 0.59. Against meningeal and miliary TB, the rate ratio in infants was 0.1. A 2014 BMJ review of 14 studies with 3,855 children found 19% protection against infection and 71% against active TB (Roy, 2014). Among children who were infected, BCG gave 58% protection against progression to disease.

BCG vaccine protection lasts up to 10 years, and it fades over time, a 2013 review found. That review of 132 studies found protection at least 15 years after vaccination in five of them. In adults, protection against lung TB differed by trial, with a rate ratio of 0.22 in the UK MRC trial (Abubakar, 2013). In the Chingleput trial the ratio was 1.05, meaning no useful benefit. CDC reported in 1996 that a BCG skin test reaction is unlikely to last more than 10 years without TB exposure⁴.

Yes: a past BCG vaccine is a known cause of a falsely positive TB skin test. No reliable method separates a BCG reaction from infection, so blood tests, which BCG does not affect, are preferred. A skin test reaction is likely for the first 2 years after newborn BCG and usually fades over time¹. CDC said in 2025 that a vaccinated person is still checked for TB infection as if never vaccinated¹. Periodic skin testing can keep the BCG reaction going longer, CDC noted in 2025¹. For a person who had BCG, the choice between PPD vs QuantiFERON blood test usually favors the blood test.

The BCG vaccine is given in the skin of the upper arm, most often to newborn babies. The US-licensed Tice strain is dropped on the skin and pushed in with a multiple-puncture device. The US label sets an adult dose of 0.2 to 0.3 mL spread over an area 1 by 2 inches⁵. Infants under 1 month get half that dose⁵. The label forbids giving this vaccine by any other route⁵. Small red bumps usually appear within 10 to 14 days⁵.

Yes, adults can get a TB vaccine, but in the US it is rarely given to them. BCG may be considered for some health care workers exposed to drug-resistant TB, case by case, after counseling. A 2014 review found unclear protection against lung TB in people vaccinated at older ages (Mangtani, 2014). The rate ratio was 0.88. CDC listed in 2025 settings where drug-resistant TB is spreading to health care workers and infection is likely¹. For most workers, regular testing for healthcare workers takes the place of a vaccine.

The expected side effect of the BCG vaccine is a small sore at the injection site that heals into a scar. Moderate swelling of lymph nodes in the armpit or neck is also expected and can last up to 3 months. CDC reported in 1996 lymph node swelling or abscess in 387 per million vaccinated infants under 1 year⁴. The rate was 25 per million in children aged 1 to 20, in the same 1996 CDC report⁴. Thick, or hypertrophic, scars form in 28% to 33% of people, and keloids in 2% to 4%⁴. The US label names spread of BCG through the body as the most serious complication⁵. It most often shows as bone infection 4 months to 2 years after vaccination⁵. Reported BCG bone infection ranged from 0.01 per million vaccinees in Japan to 43.4 per million in Finland⁴. Sweden reported 32.5 per million⁴. Fatal spread of BCG occurred at 0.06 to 1.56 cases per million doses, mostly in people with weak immune systems⁴.

People with a weak immune system should not get the BCG vaccine. CDC named in 2025 people with HIV, people likely to need an organ transplant, and pregnant women. CDC saw no harm to the fetus but said in 2025 that more studies are needed to confirm safety in pregnancy¹. The US label rules out anyone allergic to a vaccine ingredient or with a past allergic reaction to BCG⁵. The link between HIV and tuberculosis makes testing and treatment the safer path for people with HIV.

These questions cover access, countries, the vaccine itself and repeat doses.