Tuberculosis Vaccine Might Offer Some Protection Against COVID

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The best way to reduce the risk of becoming severely ill with COVID, aside from staying away from those who are infected, is to get vaccinated and stay on top of recommended boosters. If you’re immune-compromised, getting a preventive monoclonal antibody treatment (Evusheld) is also a good idea. (Double check with your doctor.) But you may be surprised to learn that vaccines designed to fight other types of respiratory infections might also give your immune system a little boost in the fight against COVID.  

Although vaccines are developed to combat a specific virus or bacteria, scientists have long suspected that they may boost the immune system in a broader way that translates to some added protection against other pathogens. This kind of protection is most likely to kick in when it comes to germs that are related (for example, those that are respiratory viruses).  

Recently, two different studies have found that people who were given the BCG vaccine, which protects against tuberculosis (TB), were less likely to get sick with COVID.  

These findings hardly mean that you should run out and get the TB vaccine, cautions Robert Popovian, PharmD, Chief Science Policy Officer at the Global Healthy Living Foundation (GHLF). For starters, COVID-specific vaccines protect far better against COVID. Plus, the TB vaccine isn’t routinely given in the U.S. 

That said, these studies are interesting, as they suggest there might be a role down the line for using the TB vaccine in combination with COVID vaccines, perhaps to bolster stronger protection or to extend the time that protection lasts. A lot more research is needed before we get to that point, however, says Dr. Popovian. 

The first study, published in Cell Reports Medicine, was a randomized trial of adults with type 1 diabetes. Ninety-six people were randomly assigned to get the TB vaccine; another 48 were assigned to get a placebo. Fifteen months later, 12.5 percent of those who got the placebo had contracted COVID, versus only 1 percent of those who had gotten the TB vaccine.  

The other study, published in Frontiers in Immunology, focused on older adults in Greece with underlying health issues like heart or lung disease. About 300 were randomly assigned to get the TB vaccine or a placebo; the researchers found that those who had gotten the TB vaccine had a 68 percent relative reduction in the risk of getting COVID.  

While these findings are interesting, they don’t directly prove that the TB vaccine protects against COVID. The studies were fairly small — COVID vaccine trials, for comparison, have included tens of thousands people — says Popovian, plus we don’t know what other protective measure (such as social distancing) those in the study might have been taking.  

Additional studies on this topic are already underway, including a large study that will follow health care workers in several countries.  

The most interesting information we have so far, says Popovian, is the fact that the TB vaccine might offer some longer-lasting protection against COVID. The research published in Cell Reports Medicine suggests that the TB vaccine might offer some protection for several decades. 

“COVID is mutating so quickly; people are blaming the lack of efficacy on the [COVID] vaccine, but the problem is the mutation rate of the virus,” he says. “Long-term, the [TB] vaccine might have potential because it has longer-lasting effects.” 

While getting the COVID vaccine is crucial, the TB vaccine — pending outcomes of future studies — could one day be used in combination with it to further reduce serious complications. “The death rate from COVID is very low right now, but more people are still dying annually from COVID in this country than they are from breast cancer,” says Popovian.  

How exactly the TB vaccine might help with COVID isn’t totally clear. But the authors of the Frontiers in Immunology study explained that two immunological processes, called heterologous T-cell immunity and trained immunity, might be responsible.  

“Heterologous T-cell responses often rely on antigenic mimicry [imitation], and recently, it has been suggested that heat shock protein 65 from BCG has sequence similarities with S-protein from SARS-CoV-2,” they wrote. Trained immunity, they added, refers to changes to the innate immune system that lead to “an increased antimicrobial activity of host defense mechanisms.” 

What This Means for You

Most people living in the U.S. do not need the TB vaccine at this time, but it’s still important to stay on top of this research and future studies that follow. In the meantime, make sure you’re working with your health care provider to stay up to date on all recommended vaccines, including the flu, pneumonia, zoster (shingles), and COVID vaccines. Read more about new vaccination guidelines for people with rheumatic disease.  

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