Tuberculosis (TB) is an infectious condition that can be fatal without treatment. It occurs following infection with the bacterium species Mycobacterium tuberculosis. The Bacille Calmette-Guérin (BCG) vaccine can help protect people from developing TB. However, in certain countries, such as the United States, health experts do not generally recommend using the vaccine.

TB is a condition that typically affects the lungs but can damage other organs. While it is uncommon in the U.S., the World Health Organization (WHO) highlights that it remains a leading cause of death in other parts of the world.

Although most TB cases occur in Asia and Africa, and the global incidence is falling, the Centers for Disease Control and Prevention (CDC) estimate that up to 13 million people in the U.S. have a TB infection. Despite this, health experts do not use the vaccine widely and only recommend it for high-risk groups, such as healthcare workers and children in certain countries.

In this article, we discuss the safety and efficacy of the BCG vaccine and who should consider getting it.

An image of a person who has had the BCG vaccine.Share on Pinterest
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TB is a contagious condition that results from an infection with the Mycobacterium tuberculosis (M.Tuberculosis) bacterium. It spreads through the air when a person with an active TB infection in the lungs coughs or speaks. Nearby individuals may then breathe in the bacterium and acquire the infection.

However, not every person with a TB infection will become ill. There are two kinds of TB-related infections: inactive or latent TB infection and active or TB disease.

In cases of latent TB, a person’s immune system can fight the bacteria and prevent progression to TB disease. In contrast, an individual with a latent TB infection will experience no symptoms and cannot spread the infection to others.

However, in other cases, the immune system cannot prevent the bacteria from multiplying. When the TB bacterium is active, experts refer to this as TB disease. In these cases, the bacterium causes people to experience symptoms such as fever, pain in the chest, and coughing up blood or sputum. People with TB disease can transmit TB to others.

The BCG vaccine has been available for more than 80 years, after French scientists Albert Calmette and Camille Guerin developed and administered the vaccine in 1921.

The BCG vaccine uses an attenuated, or weakened, strain of tuberculosis called Mycobacterium bovis, which scientists isolate from cows. This strain is similar enough to the human strain M.Tuberculosis to stimulate the immune system but not cause disease in healthy people.

Evidence suggests that the BCG vaccine is safe. However, as with any vaccine, it is possible for people to experience side effects or adverse reactions. These may include:

  • soreness at the injection site
  • a small scar at the injection site
  • fever
  • headache
  • swollen glands

While rare, more serious complications can include allergic reactions, abscesses, bone inflammation, and widespread TB.

As the BCG vaccine is a live-attenuated vaccine, 2011 guidelines recommend it is not suitable for immunocompromised or pregnant individuals.

Research suggests that the BCG vaccine is 70–80% effective against the most severe forms of TB, such as TB meningitis. However, it is less effective against the form of TB that affects the lungs.

This finding is consistent with other evidence suggesting that the vaccine has an efficacy ranging of 0–80% and an overall protective effect against TB infection of 50%. Researchers suggest that multiple factors may affect the effectiveness of the vaccine, such as differences in strains, administration method, and differences in populations and environments.

There is limited data investigating the duration of protection from BCG vaccination, with some research suggesting protection lasts for 10 years but may decline over time. However, a 2018 study investigating adults who received the vaccine as children indicates the vaccine may offer moderate protection for at least 20 years.

Health experts do not generally recommend administering the BCG vaccine in the U.S. due to the low risk of infection, variable vaccine effectiveness, and the potential interference with the TB skin test.

However, in some cases, a healthcare professional may consider a BCG vaccine following a consultation with a TB expert and if people meet specific criteria. They may also discuss the situation with the TB control program in their area.

According to the CDC, children and healthcare workers may be candidates for the BCG vaccine.

If a child is negative for a TB skin or blood test and is in frequent contact with an adult with TB disease, they may be suitable for the vaccine. Similarly, if healthcare professionals are in an environment where they interact with individuals with TB disease, they may also consider the vaccine.

Health experts in the U.S. do not recommend the BCG vaccine for the general public — instead, they opt for a targeted vaccination strategy among high-risk groups.

The CDC also specifies that the vaccine is not suitable for immunosuppressed individuals, such as those with HIV, people who may become immunosuppressed, such as those waiting for organ transplantation, in addition to pregnant individuals, due to potential complications. It is also not advisable for people with a history of TB to receive the vaccine, as they may also have a higher risk of adverse reactions to the shot.

Aside from the BCG vaccine, people can implement other TB prevention strategies. These can help stop TB infection from progressing to TB disease and may also protect others in the community. Typically, this may involve diagnostic tests to identify the type of TB infection and the use of appropriate medications.

Precautions people can take to limit the spread of TB may include:

The BCG vaccine is a preventative measure to help limit the spread of TB. It uses a weakened strain of the M.Tuberculosis bacterium to stimulate the immune system and help prevent future infections.

In the U.S., health experts do not generally recommend administering the vaccine. This is due to a low risk of infection, variable effectiveness, and possible interference with diagnostic tests. However, the vaccine may be suitable for people in high-risk groups, such as children and healthcare workers.