This Vaccine is Quietly Doing Something to Your Heart

In 2023, a Stanford researcher named Pascal Geldsetzer was looking at the way Wales had rolled out the shingles vaccine a decade earlier — and he noticed something peculiar.

To ration the limited supply, Welsh health authorities had drawn a line in the sand: if you were 79 on September 1, 2013, you qualified. If you'd already turned 80, you didn't [1].

Two people, born a week apart. Same town. Same GP. Same risk factors. One could get the vaccine. The other never could. And because Wales has detailed health records on essentially everyone, you could follow them for the next seven years and just compare what happened.

That's about as close to a randomised trial as you ever get without actually running one. And what Geldsetzer found in those records was striking enough that it ended up published in Nature, then replicated in Australia, then Canada. Earlier this year, it landed him on the TIME 100 list of the most influential people in health and medicine [2].

Table of Contents

• The New Cardiovascular Evidence
• The Healthy-Vaccinee Problem
• Why Wales Is Different
• The Bridge to the Vaccine You'll Actually Get
• What This Means for You
• Closing Thoughts
• References

This article is about something newer, and in some ways more unexpected. Because if Geldsetzer was right that this vaccine is doing something helpful to the brain, the obvious next question is: Is it helping anywhere else? And in the past year, three separate studies — including one tracking more than a million people for up to eight years — have come back with the same answer.

The shingles vaccine is associated with a substantially lower risk of heart attacks, strokes, and heart failure.

I covered the dementia side of his work in detail in a previous article — but the cardiovascular finding is new, it's bigger, and the question I want to walk you through today is whether it's actually real.

Because that headline sounds too good. Free heart protection from a shot you're already being told to get? That should make every well-trained sceptic uneasy. So today I'm going to walk you through three questions: How good is the evidence, really? What's the most plausible explanation if the effect isn't a mirage? And — most importantly — what should you actually do with this if you're 50 or older?

The New Cardiovascular Evidence

If shingles itself can damage your blood vessels — and it can — then a vaccine that stops shingles from reactivating should plausibly do something to your vascular outcomes. That's not a stretch.

The shingles virus is a herpesvirus. After a chickenpox infection in childhood, it lies dormant inside your nervous system for the rest of your life. When it reactivates — which is what causes shingles — it doesn't just damage the nerve it travels down. It can also infect the walls of blood vessels, triggering inflammation, vascular damage, and in some cases, stroke or heart attack downstream [3].

So the question stops being "why would a shingles vaccine touch the heart?" and becomes "how big is the effect, and can the studies that try to measure it actually be trusted?"

Three observational studies have come out in quick succession [4][5][6]. The strongest of them was led by a team in South Korea. Published in the European Heart Journal, their study followed more than 1.27 million adults aged 50 and older for a median of six years. They used a statistical technique called propensity-score overlap weighting to make the vaccinated and unvaccinated groups look as similar as possible at baseline [4].

The results? Those who got the vaccination had a 23% lower risk of cardiovascular events overall. Heart failure, down 26%. Major adverse events — heart attack, stroke, or death from heart disease — also down 26%. And the protective signal lasted up to eight years after vaccination [4].

That's the cleanest piece of evidence we have. A million people. Eight years of follow-up. Peer-reviewed. And — important caveat — it was the older live-attenuated version of the vaccine, not the one most of you in 2026 will actually be offered. I'll come back to that.

The second study was a systematic review, pooling nine studies. The numbers were more conservative — a 16% to 18% reduction in cardiovascular events — but the results pointed in the same direction [5].

But there's a problem with all the data that we've gone through so far. And I'm sure you'll spot it from the third study. It was a retrospective look at almost a quarter of a million US adults with established cardiovascular disease. The vaccinated group had a 46% lower risk of major adverse cardiac events in the first year post-vaccination [6].

That sounds enormous — and it should raise eyebrows. The same study reported a 66% reduction in all-cause deaths in the first year after a single vaccination. These numbers are far larger than what's typically seen even with established cardiovascular therapies [6].

And that 66% mortality figure isn't just impressive. It's doing something the rest of the data isn't. It's giving the game away — and I'm sure you've already spotted the issue.

The Healthy-Vaccinee Problem

People who choose to get a non-mandatory vaccine are not a random slice of the population. They're more likely to see their GP regularly. They're more likely to take their medications. They tend to have higher socio-economic status, lower smoking rates, and better preventive-care engagement across the board.

In epidemiology, this is called healthy user bias. And it's the standard alternative explanation for any observational study showing a vaccine protects you against something the vaccine wasn't designed for.

The three studies I just walked you through — the Korean one, the ESC meta-analysis, the ACC abstract — all share the same fundamental weakness.

But here's where it gets interesting. Because if healthy-user bias were the whole story, you'd expect the benefit to show up most clearly in the healthiest people — the ones whose baseline behaviours are already driving the effect. In the Korean study, the opposite happened.

The people who benefited most from vaccination were the ones with unhealthy baseline behaviours [4].

That's hard to square with a pure selection effect. If vaccination were just a proxy for being healthy, the unhealthy subgroup is exactly where you'd expect the signal to wash out. Instead, it's where the signal was strongest.

That doesn't settle the question. Selection effects can hide inside subgroups — the smoker who gets vaccinated may still be more engaged with healthcare than the smoker who doesn't. But it does introduce a note of caution about the "this is all just the healthy user bias" explanation.

To figure out if we're seeing a true causal relationship here, we need a randomized controlled trial. And that's where the work that put Geldsetzer on the TIME 100 comes in.

Why Wales Is Different

Remember the line in the sand with the vaccine rollout in Wales at the start of this article?

Born before the 2nd of September 1933 — never eligible. Born on or after — eligible.

That cutoff didn't care about your health behaviours. It didn't care whether you saw your GP. It didn't care whether you smoked or exercised. It cared about a single date on your birth certificate. And in the dementia analysis Geldsetzer's team published in Nature last year, eligibility for the vaccine produced a substantial protective effect on dementia diagnoses — about a 20% relative reduction [7].

I covered that finding in detail in a previous article.

The point that matters here is structural, not clinical. If the vaccine produces a real biological effect on a major outcome in a study where healthy user bias has been engineered out by design, that lends weight to the cardiovascular signal showing up in the messier observational studies. Different organ. Different research teams. Different countries. Different datasets. Same direction.

The Bridge to the Vaccine You'll Actually Get

Now I have to flag something crucial, because if I don't, the comments will. Almost everything I've described to you so far — the Korean study, the Welsh natural experiment, most of the dementia work — used the older shingles vaccine, called Zostavax. A live, weakened virus.

That vaccine has been retired in most of the world. CDC guidelines in the U.S., for instance, specify the recombinant vaccine, Shingrix. The older Zostavax was phased out in 2020 [8].

Shingrix is a fundamentally different product. It has a different antigen — just a piece of the virus, not the whole thing — and a powerful adjuvant called AS01 designed to provoke a stronger immune response. So a fair question is: do the off-target benefits seen with Zostavax carry over to the vaccine you're going to be offered today?

The honest answer is: probably yes, but our evidence here is one notch weaker.

An Oxford team led by Maxime Taquet used the moment in 2017 when the United States switched from Zostavax to Shingrix as a quasi-natural experiment. They compared roughly 100,000 Shingrix recipients to roughly 100,000 Zostavax recipients, matched on baseline characteristics, and followed them for six years. Shingrix was associated with about 17% more dementia-free time than Zostavax — meaning, in this dataset, Shingrix looked at least as protective, and maybe more so [9].

Two caveats on that. First, this is observational again. Second, one of the senior authors has a consulting relationship with GSK, the manufacturer of Shingrix. The team says GSK had no role in this specific study, and I take them at their word — but it's the kind of thing you should know [9].

What This Means for You

So where to from here? Well, here's what I advise my patients.

If you're 50 or older and you haven't been vaccinated against shingles, the case for getting Shingrix has just gotten stronger. The original reason — preventing a painful, sometimes disabling rash and the lingering nerve pain that can follow it — was already a reasonable one. The dementia signal added weight. The cardiovascular signal adds more.

In the United States, the CDC recommends two doses of Shingrix, two to six months apart, for all adults aged 50 and up with normal immune function [8].

One thing your GP may not emphasise enough: Shingrix is, to put it politely, a vaccine you'll feel. The injection-site soreness, fatigue, headache, and sometimes fever are common after both doses. Roughly one in six recipients had reactions severe enough to interfere with daily activities [10].

That's not an emergency — it's the immune system doing what the adjuvant is designed to make it do — but it's worth knowing in advance. Practical tip: book your second dose for a Friday afternoon, so the worst of the reaction lands on a Saturday and not in the middle of a workweek.

If you've already had the older Zostavax vaccine years ago, the CDC recommends getting the two-dose Shingrix course anyway [8].

Shingrix is more effective at preventing shingles itself, and the off-target evidence we have for the recombinant vaccine looks at least as strong [11].

What I would not tell my patients is that this is a reason to chase down a vaccine you're not yet eligible for. The evidence base is strong enough to be another reason not to skip Shingrix when your turn comes. It is not yet strong enough to recommend off-label vaccination of 40-year-olds. There's a real difference, and I want to be careful about it.

Closing Thoughts

There's one detail about Geldsetzer's work I want to leave you with. When he first noticed the Welsh birthdate cutoff in those records, he wasn't looking for a vaccine that lowered dementia. He was looking at how policy decisions get made when supplies are limited. The dementia finding came as a surprise to him. The cardiovascular finding came as a surprise to a different team in Korea, looking at a completely different population. Sometimes the most useful evidence in medicine doesn't come from the trial that was designed to find it.

It comes from a date on a birth certificate. From a propensity-weighted spreadsheet of a million people in a country whose government tracks vaccinations against insurance claims. From an accident.

References

1. https://med.stanford.edu/news/all-news/2025/03/shingles-vaccination-dementia.html

2. https://time.com/collections/time100-health-2026/7362629/pascal-geldsetzer/

3. https://pmc.ncbi.nlm.nih.gov/articles/PMC5298244/

4. https://academic.oup.com/eurheartj/article/46/30/2991/8124786

5. https://academic.oup.com/eurheartj/article/46/Supplement_1/ehaf784.3633/8312335

6. https://www.acc.org/About-ACC/Press-Releases/2026/03/16/19/33/Shingles-Vaccine-Drastically-Cuts-Risk-of-Serious-Cardiac-Events

7. https://www.nature.com/articles/s41586-025-08800-x

8. https://www.cdc.gov/shingles/hcp/vaccine-considerations/index.html

9. https://www.nature.com/articles/s41591-024-03201-5

10. https://www.cdc.gov/vaccine-safety/vaccines/shingles-herpes.html

11. https://www.bmj.com/content/363/bmj.k4029