In the UK my GP is sending out emails suggesting I take this vaccine. At the moment my rapamycin levels are too high, but I may do it.
chatGPT:
Tidy transcript
Topic: Could the shingles vaccine reduce cardiovascular risk as well as shingles and dementia risk?
Source transcript:
In 2023, Stanford researcher Pascal Geldsetzer was looking at how Wales had rolled out its shingles vaccine a decade earlier. Welsh health authorities had used a strict age cut-off because supply was limited. If someone was 79 on 1 September 2013, they qualified; if they had already turned 80, they did not.
That meant two people born only a week apart, living in the same town, with the same GP and the same risk factors, could be treated differently: one could receive the vaccine and the other could not. Because Wales has detailed health records for essentially everyone, researchers could follow these people for the next seven years. This created something close to a randomized trial, even though no trial had been deliberately run.
Geldsetzer’s team found that shingles vaccination was associated with a lower risk of dementia. That finding was published in Nature and has since attracted attention because the Welsh age cut-off created a relatively strong natural experiment. The Nature paper reported about a 20% relative reduction in new dementia diagnoses over seven years among those receiving the zoster vaccine. (Nature)
The video then turns to a newer question: if the shingles vaccine appears to have effects on the brain, might it also affect the cardiovascular system? Three recent studies have suggested that shingles vaccination is associated with a lower risk of heart attacks, strokes and heart failure.
The biological rationale is that shingles is caused by varicella-zoster virus, a herpesvirus. After chickenpox, the virus remains dormant in the nervous system. When it reactivates, it can cause shingles, but it may also affect blood vessels by provoking inflammation and vascular damage. That makes it plausible that preventing shingles reactivation might reduce some cardiovascular events.
The strongest cardiovascular study discussed was from South Korea. It followed more than 1.27 million adults aged 50 and older for a median of about six years. The study used propensity-score overlap weighting to make vaccinated and unvaccinated groups more comparable. Vaccinated people had a 23% lower risk of cardiovascular events overall, a 26% lower risk of major cardiovascular events, and a 26% lower risk of heart failure. The apparent protective signal lasted up to eight years. (European Society of Cardiology)
However, the vaccine used in that Korean study was the older live attenuated zoster vaccine, not the current recombinant vaccine, Shingrix, now used in many countries.
The video then discusses the main problem with the evidence: these are mostly observational studies. People who choose to get non-mandatory vaccines tend to be different from those who do not. They may see doctors more regularly, take medications more reliably, smoke less, have higher socioeconomic status, and receive better preventive care. This is called healthy-user bias.
A US retrospective study in people with established cardiovascular disease found a very large apparent reduction in major cardiovascular events after vaccination, but it also found a 66% reduction in all-cause mortality in the first year. The video argues that this number is so large that it likely reveals residual confounding: vaccinated people were probably healthier or better connected to healthcare in ways the study could not fully adjust for.
The Korean study is presented as more interesting because the apparent benefit was strongest in people with less healthy baseline behaviours. That pattern is harder to explain by simple healthy-user bias, although it still does not prove causality.
The video then returns to the Welsh natural experiment. In that case, vaccine eligibility depended on a birth-date cut-off, not on whether someone was health-conscious. That makes the dementia finding more credible than a standard observational association.
The video also addresses the difference between old and new vaccines. The older vaccine was Zostavax, a live weakened-virus vaccine. It has been retired in many countries. The newer vaccine, Shingrix, is recombinant: it contains a viral component plus an adjuvant rather than a live virus. CDC guidance recommends two doses of Shingrix for immunocompetent adults aged 50 and over, including people who previously received Zostavax. (CDC)
An Oxford-led study used the 2017 US switch from Zostavax to Shingrix as a quasi-natural experiment. It compared roughly 100,000 Shingrix recipients with roughly 100,000 Zostavax recipients and found that Shingrix was associated with more dementia-free time than Zostavax. The reported figure was about a 17% increase in diagnosis-free time. (Nature)
The practical advice in the video is that people aged 50 or older who are eligible for shingles vaccination have stronger reasons to take it: prevention of shingles, post-herpetic neuralgia, possible dementia protection, and now possible cardiovascular protection. But the video warns that the evidence is not strong enough to justify people outside recommended age groups chasing the vaccine off-label.
It also notes that Shingrix can be reactogenic. Injection-site soreness, fatigue, headache and fever are common, and some people have symptoms strong enough to disrupt daily activities for a day or so.
For a UK viewer, the eligibility point needs adjusting: the NHS does not simply offer shingles vaccination to everyone aged 50 and over. NHS eligibility currently includes adults turning 65, people aged 70 to 79, and adults aged 18 or over with a severely weakened immune system. (nhs.uk)
Summary
The video argues that shingles vaccination may have benefits beyond preventing shingles itself. The core claim is that varicella-zoster virus can damage blood vessels when it reactivates, so preventing reactivation could plausibly reduce cardiovascular events. The video presents three lines of evidence: observational cardiovascular studies, the Welsh dementia natural experiment, and comparative data suggesting Shingrix may be at least as protective as Zostavax for dementia.
The main cardiovascular evidence is a South Korean study of more than 1.27 million adults aged 50 and older. It found lower rates of overall cardiovascular events, major adverse cardiovascular events, and heart failure among vaccinated people. The video treats this as suggestive but not conclusive because the study was observational.
The video’s central caution is healthy-user bias. People who get optional vaccines are often healthier, wealthier, more medically engaged, and more adherent to treatment. A very large mortality reduction in one US observational study is treated as a warning sign that confounding may be inflating the apparent benefit.
The final recommendation is moderate: eligible people should not skip Shingrix, but the evidence does not yet justify off-label vaccination in younger, ineligible people purely for heart or dementia protection.
Critique
The video is strongest when it distinguishes plausibility from proof. It does not simply say “the shingles vaccine prevents heart attacks”; it acknowledges that observational vaccine studies are especially prone to healthy-user bias. That is an important caveat.
The biological mechanism is plausible. Shingles reactivation can involve inflammation and vascular injury, and shingles has been linked to increased short-term risks of stroke and myocardial infarction. Therefore, a vaccine that prevents reactivation could reasonably reduce downstream cardiovascular events. But plausibility does not establish the size of the effect.
The Korean cardiovascular study is large and impressive, but it is still not randomized. Propensity-score methods can balance measured variables, but they cannot fully deal with unmeasured differences such as frailty, healthcare-seeking behaviour, medication adherence, diet, income, or GP engagement. A 23–26% cardiovascular risk reduction is large enough to deserve serious attention, but also large enough to require caution.
The video correctly flags that the strongest dementia evidence comes from the Welsh birth-date cut-off design. That is much closer to causal evidence than ordinary observational matching. However, that natural experiment was about dementia, not cardiovascular events. It strengthens the general idea that zoster vaccination may have off-target effects, but it does not by itself prove the heart-disease claim.
The biggest limitation is extrapolation from Zostavax to Shingrix. Many of the cardiovascular findings involve the older live vaccine. Shingrix is immunologically different, more effective against shingles, and uses a strong adjuvant. It may well produce similar or greater off-target benefits, but the cardiovascular evidence for Shingrix specifically is weaker than the evidence for shingles prevention.
The video’s practical advice is reasonable, but it is framed more around US-style eligibility. In the UK, NHS access is narrower and age-band based, so “if you are 50 or older” is not the same as “you are eligible.” For a UK patient, the more accurate conclusion is: take Shingrix if you are NHS-eligible or clinically advised to do so; do not treat the cardiovascular findings as settled proof or as a reason to bypass eligibility rules.
Overall, the video gives a good sceptical interpretation of an interesting signal. The best conclusion is that shingles vaccination has a strong established indication, with plausible but not yet definitive evidence of cardiovascular and dementia benefits.