A growing body of research suggests Shingrix can delay dementia and reduce the risk of cardiovascular events. Doctors want more proof.

Doctors say they want to see stronger data about the shingles vaccine's purported heart benefits.

Biohackers are turning to the shingles vaccine to ward off heart issues and delay dementia, but doctors want to see clinical evidence from rigorous medical studies before making the case to their patients.

A new study, published last month in Nature Medicine, found that GSK's (UK:GSK) (GSK) Shingrix lessened the risk of ischemic heart disease by 10% over seven years and heart failure by 12% in Americans who were at least 60 years old, when compared with people who received an older shingles vaccine that's no longer available in the U.S.

The study, led by the University of Oxford, is one of several observational studies that have found wide-ranging health benefits associated with the vaccine beyond preventing shingles, a painful blistering skin infection caused by the same virus that causes chickenpox. Another study, conducted by some of the same University of Oxford researchers and published in 2024, found Shingrix could delay dementia diagnoses by about six months. (One of the researchers is a consultant for GSK, but the drugmaker was not involved in the heart disease or dementia studies.) Other research found the older vaccine may slow the biological aging process and reduce all-cause mortality.

These studies are fueling the idea that Shingrix is a wonder vaccine. It's popular among longevity influencers like Bryan Johnson, who said this year that he was getting the shingles vaccine for its potential longevity benefits, and David Sinclair, a researcher who declared the vaccine is associated "with better health and longevity long-term."

But doctors are skeptical, saying stronger evidence is needed, ideally from randomized and placebo-controlled clinical trials, to make the case that the purported benefits are real.

"It's encouraging from a clinical perspective, but as you talk with any scientist, you know we have to be cautious about framing the evidence," said Thomas Caprio, chief of geriatrics and palliative care at the University of Rochester Medicine hospital system. "It shows that there's a potential additional benefit."

That evidence gathering is under way. During an earnings call in July, GSK revealed that it plans to run a Phase 3 trial evaluating whether Shingrix can reduce the risk of major adverse cardiac events in 16,000 adults who have or are at risk for heart disease. But patients and doctors will have to wait several years until there's data to share from that study.

"It certainly cannot ever be used to say: It's likely to reduce your risk of heart disease, or it prevents the risk of heart disease, or reduces the risk. You cannot say any of those three statements," said David Nace, chief of geriatric medicine at the UPMC hospital system in Pittsburgh. "All we can say is some studies have suggested this, but we have no reason to believe that that is actually true."

The Food and Drug Administration approved Shingrix, a recombinant vaccine, in 2017, and it quickly became the go-to shingles vaccine after its launch in early 2018. By 2020, Merck (MRK) had discontinued Zostavax, a live attenuated virus vaccine that was approved in 2006.

The U.S. currently recommends both doses of Shingrix, now the only shingles vaccine available in the U.S., for all adults who are at least 50 years old, and for those at least 18 years old who have an immunodeficiency or are taking an immunosuppressant.

Even as the research has accumulated, that hasn't translated to more people receiving the vaccine. Only about 24% of Americans who should get the vaccine have had both doses, according to a Centers for Disease Control and Prevention survey in 2023.

It's unclear why uptake is so low, although physicians say the shingles vaccine is less of a priority for older adults than the shots for COVID-19, pneumonia or the flu, all of which are more deadly than shingles. While it is painful and frustrating, shingles rarely leads to hospitalizations and causes fewer than 100 deaths a year in the U.S., according to the CDC. For healthy adults between the ages of 50 and 69, the vaccine is 97% effective at preventing shingles and about 90% effective at preventing postherpetic neuralgia, a persistent and painful nerve condition that continues after shingles goes away.

"We have to be thoughtful and careful and not overcommunicate the criticalness of some vaccines versus others," Nace said, "and we should never overcommunicate potential benefits when we don't know that they exist."

The need for better clinical data

In the new study, the researchers looked at the medical records of 72,000 Americans, half of whom predominantly received Zostavax in 2017, when that vaccine was the standard of care. The other half were administered Shingrix during the same five months in 2018.

They found that the group who took Shingrix had a lower risk of cardiovascular events over the next seven years compared with those who received Zostavax. There was no difference in risk reduction by gender, although men had a lowered risk of ischemic stroke.

Several observational studies have found the shingles vaccines may have a benefit for people with heart disease. Research released this year at a major cardiology conference found that people with heart disease who received Shingrix or Zostavax had about half the rate of serious cardiac events after a year compared with those who did not get either shot. Another study, published last year in the European Heart Journal, found that getting a live attenuated virus vaccine like Zostavax led to a 23% reduction in the risk of cardiovascular events like stroke or heart failure in adults in South Korea.

As promising as these studies appear, they were all conducted in a similar manner - by examining older medical records. Conducting a trial that is randomized and placebo-controlled, meaning some participants will get the vaccine and others will get a placebo, helps eliminate the "healthy volunteer effect" commonly seen in observational studies.

In observational studies, which look back at how patients behaved naturally, it can be hard to separate whether the intervention or someone's lifestyle is responsible for the benefits. Doctors say Americans who get vaccines tend to be healthier than those who do not, and people who ask their doctors about whether to get the shingles vaccine are more likely to be health conscious.

"Nothing's conclusive until it's randomized," said Ben Hirsh, director of preventive cardiology at the Sandra Atlas Bass Heart Hospital in Manhasset, N.Y.

The other unknown is the mechanism by which Shingrix or other shingles vaccines may reduce the risk of heart disease. One theory is that the vaccine helps lessen the inflammation brought on by the virus, potentially through interleukin-6, a protein involved in the body's inflammatory response, according to Hirsh.

"There is a theoretically plausible benefit in that the vaccine does target IL-6, and IL-6 is implicated in heart disease, in the greater likelihood of having heart-disease events," he said.

GSK shared a similar perspective.

"It could possibly be dialing down inflammation more broadly, including the kind of age-related inflammation that builds up in the brain," Sanjay Gurunathan, GSK's global head of vaccines and infectious disease research and development, said during the company's earnings call. "If that's right, it could mean Shingrix is nudging the whole trajectory of neuroinflammation in a healthier direction."

The trial is expected to start recruiting patients later this year, according to a GSK spokesperson. If it succeeds, GSK told investors that it plans to submit the vaccine to the FDA for an updated label in 2029 at the earliest. That would be a major move for the drugmaker. Shingrix is its top-selling drug, although sales have been declining in the U.S.

For now, however, doctors suggest that Americans address their heart health with tried-and-true methods like exercising more, not smoking, and controlling their blood pressure, according to Caprio.

"People should not be seeking these vaccines just because they think they're going to protect their heart," he said. "There's other things that they should be doing in terms of a healthy lifestyle."

-Jaimy Lee