There’s a vaccine available for tuberculosis. However, it’s not commonly given in the United States. One reason why is that tuberculosis is no longer as common in the United States as it once was.

Tuberculosis (TB) is an infection caused by the bacteria Mycobacterium tuberculosis. It most often affects the lungs. It’s contagious, meaning that it can be transmitted from person to person.

This article will go into more detail about the TB vaccine, who needs it, and what to know about its safety and effectiveness.

The TB vaccine is called Bacillus Calmette-Guérin (BCG). It’s made from a weakened form of the bacterium Mycobacterium bovis, which causes a TB-like illness in cattle.

Exposure to BCG can help your body generate an immune response against M. tuberculosis, which causes TB in humans.

According to the Centers for Disease Control and Prevention (CDC), BCG isn’t typically recommended in the United States. This is due to:

  • the low risk of contracting TB in the United States
  • variations in the effectiveness of BCG to prevent TB in adults
  • the possibility of BCG interfering with tuberculin skin tests, which are used to detect TB infections

After a consultation with a doctor experienced in TB, BCG may be recommended for:

  • children who do not have TB but are often exposed to TB, or cannot be separated from an adult who:
    • hasn’t been treated for TB, or
    • has drug-resistant TB
  • healthcare professionals who are working in areas where there’s a high percentage of people with TB or ongoing TB transmission, especially of drug-resistant strains

In countries where TB is more common, BCG is still widely used. According to the World Health Organization (WHO), BCG is given to more than 80% of all newborns and infants in countries where it’s a part of a national immunization program.

In countries where TB is common, BCG is mainly used to protect against two types of severe TB in infants and young children: TB meningitis and disseminated TB.

Against these types of TB, BCG provides up to 80% protection.

However, this protection doesn’t last forever. A 2022 study found that BCG vaccination at birth only provided significant protection against any type of TB to children under 5 years old. It was not effective for older children and adults.

A 2016 study looked into the effectiveness of BCG in protecting against pulmonary (lung) TB. Researchers found that vaccine effectiveness against this specific type of TB became statistically insignificant 20 years after vaccination.

As you may have noticed, the vaccine effectiveness estimates for BCG in adults are highly variable. According to one 2021 review of research, studies have found that the effectiveness of BCG in adults has ranged from zero to 80%.

While more research is needed to help explain this large variation, scientists have some ideas about why this happens, such as:

  • exposure to other Mycobacterium species in the environment masking or blocking an immune response to BCG
  • immune system or genetic variations between people
  • differences between the strains of BCG used to make the vaccine

Like many vaccines, BCG can cause side effects. The most common are skin changes at the vaccination site.

Many people who receive the BCG vaccine develop a pustule or blister at the vaccination site. This typically appears 10 to 14 days after vaccination. It can be present for 4 to 6 weeks before it goes away.

Other potential side effects of the BCG vaccine include:

There are also some more serious, although rare, side effects of the BCG vaccine, including:

Is there anyone who shouldn’t receive BCG?

Some people should not receive BCG, such as:

  • People with a weakened immune system: BCG is a live vaccine and can cause potentially serious problems for people with a weakened immune system. You may have a weakened immune system if you:
    • are living with HIV
  • Pregnant people: According to the BCG package insert, although no harmful effects to a developing fetus have been seen, reproduction studies haven’t been done. As such, BCG isn’t currently recommended for pregnant people.
  • Allergies: If you have a known allergy to any component of the BCG vaccine, it’s not recommended that you get it.

The rate of TB in the United States is low. According to the CDC, a total of 7,174 cases of TB were reported in 2020.

While TB isn’t a large public health threat in the United States, that’s not the case for many other parts of the world.

According to the WHO, a total of 10 million people across the globe fell ill with TB in 2020. There were also 1.5 million deaths from TB worldwide in 2020.

The WHO also notes that 30 countries with high TB levels account for most new TB cases. Countries that are especially impacted include:

  • India
  • China
  • Indonesia
  • the Philippines
  • Pakistan
  • Nigeria
  • Bangladesh
  • South Africa

Researchers are working to develop a newer, more effective TB vaccine. However, the lack of understanding about why exactly BCG is so variable in effectiveness makes designing a new vaccine quite challenging.

A 2022 review notes that at least 14 new vaccines for TB are in clinical development. These use different types of vaccine technology, including:

  • live, which uses a weakened form of a germ
  • subunit, which uses only a piece of a germ
  • viral vector, which uses a modified virus to deliver the vaccine contents

The success of the mRNA vaccines for COVID-19 has also sparked interest in using the same technology to develop a TB vaccine. In fact, a 2022 paper has already proposed a potential mRNA construct to begin testing in laboratory studies.

BCG is currently the only vaccine for TB. Because TB isn’t common in the United States, it’s not typically recommended for use in the country. However, it’s still a widely used vaccine in many other parts of the world.

BCG is mainly given to infants and young children to help protect them from very severe forms of TB. When used in this context, it’s very effective. However, BCG isn’t very protective in older children, adolescents, and adults.

This variation in effectiveness is driving a search for a newer, more effective TB vaccine. Researchers are exploring many technologies to achieve this, including mRNA vaccine technology.