New research suggests future applications


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Research suggests that the 100-year-old BCG tuberculosis vaccine could provide clues to the development of future vaccines and personalized treatments. Cara Dolan/Stocksy United
  • The tuberculosis vaccine was originally developed in 1921 and is still used today.
  • Researchers recently compared the effects of TB vaccines in infants with laboratory studies.
  • The biomarkers they discovered could be used to develop new, more effective vaccines.

Tuberculosis (TB) is an infection caused by bacteria Mycobacterium tuberculosis which most often affects your lungs. According to the World Health Organization, it is the second infectious cause of death worldwide behind COVID-19.

Perhaps the most tragic thing about this statistic is that the TB vaccine has been around for over a hundred years.

The Bacille Calmette-Guérin (BCG) vaccine – named after its developers, Albert Calmette and Camille Guérin – was first administered in 1921, and it remains the only vaccine against tuberculosis to this day.

So how does it work, what can we learn from it, and perhaps most importantly, do you need to have it?

The BCG vaccine is called a live attenuated vaccine. This means that it contains a weakened – but mostly still alive – sample of the bacteria that causes tuberculosis.

By fighting off this weakened version of the bacteria, your body learns to identify it and defeat it if it encounters it again. This is what we generally call immunity, but it is not the only method to induce it.

Dr. Danelle Fisher, FAAP, pediatrician and chair of pediatrics at Providence Saint John’s Health Center in Santa Monica, Calif., told Healthline that there are many types of vaccines that don’t use a live pathogen. Examples include:

  • inactivated vaccines containing killed pathogens
  • toxoid vaccines containing inactivated toxins produced by pathogens
  • subunit vaccines containing only the identifiers of a pathogen instead of the whole
  • conjugate vaccines containing the sugar-like polysaccharides that coat bacteria to elicit an immune response
  • viral vector vaccines containing a harmless modified virus that creates the identifying features of a pathogen in your own body
  • mRNA vaccines trick your own cells into producing identifying bits of a pathogen that your body can learn from

mRNA vaccines have gotten a lot of attention lately, as many COVID-19 vaccines have used this method.

Dr. Charles Bailey, medical director of infection control at Providence St. Joseph’s Hospital and Providence Mission Hospital in Southern California, told Healthline that live-attenuated vaccines like the BCG vaccine are still common.

“Other live attenuated vaccines include those for measles, mumps, rubella, varicella, typhoid (oral) and yellow fever,” Bailey said.

While some live attenuated vaccines are on CDC child and adolescent vaccination scheduleBCG is not one of them.

Does this mean that it is not effective? Not at all. In fact, there are many effective vaccines that are not routinely given in the United States.

“There may be potential for over-vaccination to ‘exhaust’ the immune system,” Bailey said.

“The use of vaccines should be with the expectation of benefit that outweighs any potential risk of treatment. Although vaccines are relatively safe and certainly prevent far more negative outcomes than they could cause, they are not not completely risk-free,” he added.

It is therefore important to focus on the vaccines that will have the greatest impact. Tuberculosis is no longer widespread enough in the United States to widely vaccinate against it.

The BCG vaccine is generally only recommended for people living in areas where TB is more common or for health workers who may be treating patients with TB. Eight countriesled by India, China and Indonesia, account for two-thirds of all TB cases.

Although the BCG vaccine has been around for a long time, our understanding of the human body is constantly evolving. This presents an opportunity for researchers to look at time-tested treatments through a modern lens.

In a study published in the journal Cell reports, experts studied blood samples from infants in Guinea-Bissau before and after receiving the BCG vaccine. These samples were compared to cord blood donated in Boston that had been treated with the BCG vaccine in the laboratory.

The results were twofold.

First, they were able to detect changes in metabolic markers, specifically certain lipids (fats), in infant blood samples that correlated with an immune response to the BCG vaccine. This had never been shown before and could be used to help future research into exactly how the BCG vaccine works to protect against tuberculosis.

Second, the test results on the infants matched the test results from the lab work. This means that future vaccine studies could be conducted in a laboratory with a higher degree of certainty that they would be equally effective in living people.

“It’s an interesting finding in that metabolic markers can end up being a clue to how each individual responds to a vaccine,” Fisher said.

Doctors may one day be able to use these markers to help determine more precisely how different people will react to specific vaccines. This could help spur future vaccine development or further reduce the incidence of adverse effects, but it’s also important to keep things in perspective and remember that a lot more research is needed.

“This may be something to investigate and track, [but] as with all preliminary findings, this should be validated by repeated studies,” Bailey said.

What the next hundred years of medicine will bring, only time can tell.

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