Dr. Vinay Prasad takes hammer and tongs to the idea that the shingles vaccine reduces dementia/AD. He focuses on shingles, but also mentions that this likely applies to all vaccines. He examines new studies, the original Wales study, and the observational studies. We may agree or not, but either way one needs to present credible contradictory evidence and reasoning. Like him or hate him, at the moment he’s probably my favorite analyst of studies on yt… or almost anywhere else for that matter. It is strict evidence that rules, nothing else - dura lex, sed lex.
Does the Shingles Vaccine Reduce Dementia? No! (via Vinay Prasad MD MPH)
I would reframe the question. Does the shingles vaccine reduce or eliminate the symptoms of a shingles infection? Yes, the vaccine is 90% effective. A full-blown infection involves a tell-tale rash, severe itching, extreme exhaustion, and burning pain from postherpetic neuralgia. Other symptoms such as a headache, fever, confusion, and seizures induce a state of near madness in the victim, resulting in personality changes, memory loss, and cognitive decline.
Asked Google “dr. vinay prasad should his opinion be trusted”. Generally, “no”. He seems to be chasing views on social media platforms by offering contrarian opinions based upon little to no research.
The observational studies can be thrown in the trash can and doesn’t prove anything, but the natural experiment in Wales was interesting. If the new pre-print methodology is good for both Wales and England, that means the result wasn’t replicated, and who knows why.
Overall I’ve gone from 75% → 25% probability that shingles vaccine reduce dementia risk by 1/5, until more definitive evidence. The two upcoming RCT’s sound interesting.
Talk about cherry picking articles and the messenger has a really jaded past. He claims others are political but his whole viewpoint is that the experts are wrong on everything.
You have to wonder about anyone who gets hired and takes the job with the Trump admin in the FDA and then you have to also be unique to get fired twice from that same administration. Although after seeing that video, I certainly understand his terminations.
There are tons of papers showing reduced dementia rates including date changes on vaccine type in populations with nearly universal uptake. Mostly it is the US has such differences in populations that get vaccines.
The Wales controlled naturalistic experiment caught my attention and led to my examining both the mechanistic speculations (which have merit generalized from more settled research) and the lower level observational data, some of which is difficult to explain in alternatives. Nothing in Prasad’s case altered that interpretation. Results from current studies should help us sort this out.
Importance Recent evidence from a quasi-experiment in Wales showed that herpes zoster (HZ) vaccination appears to prevent or delay dementia. Exploiting a similar quasi-experiment in Australia, this study investigated the effect of HZ vaccination on dementia occurrence in a different population and health system setting.
Objective To determine the effect of HZ vaccination on the probability of receiving a new diagnosis of dementia.
Design, Setting, and Participants In Australia, starting November 1, 2016, live attenuated HZ vaccination was provided free to individuals aged 70 to 79 years through primary care clinicians. Thus, individuals whose 80th birthday was just a few weeks before November 1, 2016, never became eligible, whereas those whose 80th birthday was just a few weeks later were eligible. The key strength of this quasi-experiment is that one would not expect that these comparison groups who differ in age only minutely would, on average, differ in any health characteristics and behaviors. Primary health care records were analyzed with week-of-birth information from 65 general practices across Australia, using a regression discontinuity design.
Exposure Eligibility for HZ vaccination based on date of birth.
Main Outcome New diagnoses of dementia as recorded in primary care electronic health record data.
Results In this sample of 101 219 patients, 52.7% were women and mean age was 62.6 years (SD, 9.3 years) as of November 1, 2016. Individuals born just before vs just after the date-of-birth eligibility threshold (November 2, 1936) for HZ vaccination were well balanced in their past preventive health services uptake and past chronic disease diagnoses. There was an abrupt increase of 16.4 percentage points (95% CI, 13.2-19.5; P < .001) in the probability of ever receiving HZ vaccination between patients born shortly before vs shortly after the date-of-birth eligibility threshold. The eligibility rules of the HZ vaccination program thus created comparison groups born just on either side of the date-of-birth eligibility threshold who were likely similar to each other, except for a large difference in their probability of receiving the intervention (HZ vaccination) of interest. This study found that eligibility for HZ vaccination (ie, being born shortly after vs shortly before November 2, 1936) decreased the probability of receiving a new dementia diagnosis during 7.4 years by 1.8 percentage points (95% CI, 0.4-3.3 percentage points; P = .01). Being eligible for HZ vaccination did not affect the probability of taking up other preventive health services (including other vaccinations) or the probability of receiving a diagnosis of common chronic conditions other than dementia.
Conclusions and Relevance By taking advantage of a quasi-experiment and corroborating findings from Wales in a different population, this study provides evidence of the potential benefits of HZ vaccination for dementia that is more likely to be causal than that of more commonly conducted associational studies.
Gee, what a surprise. He’s against vaccines so he will damn any data out there that supports them. There’s a reason that the US is experiencing the worst outbreak of measles in many decades. There’s a reason thousands are dying in Africa from HIV/AIDS. There’s a reason that so much science is being eviscerated. Trump, RFK, Prasad, and the others have taken control and moving us so far backwards we may never recover.
Sorry for the politics but I cannot help it. These types–Trump et al–are literally killing people.
And by the way, the VZV vaccine data is pretty damn strong.
I’m as disgusted by the health policies of this administration (and to be fair many policies of previous administrations) as anyone. But, we must remain fair, so that we don’t accidentally assign blame where it does not belong.
Vijay Prasad is a highly respected doctor, educator and researcher. Here is a challenge: you will not find one critic of his who is the least credible themselves. He is pretty universally acknowledged to be one of the best in his field. He was hired into this administration by someone who himself was one of the few people with insight and integrity in the administration. It was a giant (and good!) surprise to all. Soon both he an Vijay were gone, precisely because they retained their integrity and refused to shill for policies they disagreed with.
Also, he is most definitely not “against vaccines”. He is however very clear eyed about policy mistakes and limitations around their deployment (specifically covid 19). Things like school closures and the like. And in this, he was shown to have been right. The thing to understand about him, is that he is extremely evidence based, and will not compromise to be a “team player”, which earns him enemies on both sides. He will not advocate or rubber stamp policies because it’s simpler to get populations to go along even if the truth is distorted “for the public good” (like in the masking scandal). He will not go along to get along - he goes by evidence.
Now, he may still be mistaken about something (aren’t we all!), but the way to tackle such disagreements is strictly through arguments from evidence. Instead, we have attacks based on personality objections - note how this works, even here… instead of tackling the argument, it’s tackling the person.
He’s worth listening to, even if you disagree. Listen to what he says and make up your own mind, don’t listen to personality based opinions. I myself have found him to argue with integrity, even if I have not agreed with every argument 100% (which I wouldn’t expect to anyway).
Anyhow, my personal bias (we all have them) is to be particularly vigilant about things I’d like to be true (rapamycin works in humans, vaccines reduce dementia etc.), and so seek out and listen attentively to critics and contrary evidence, because I know how easy it is to fall in love with what we want to hear, and that is a path away from truth and into a cult. Perhaps that leads me to a slight overvaluing of contrary viewpoints - and that is my bias. But in the end: it is the Truth that matters.
Credentials. He did a fellowship in heme/onc and until he found his contrarían view in 2020, he worked on cancer treatment.
He is not an immunologist, virologist or neurologist. What expertise in herpesvirus, the immunologic response or dementia does he have? Yes, yes, he has clinical trial experience but using chemotherapy is a much different environment than preventing dementia. You have to be dogmatic about RCTs for chemotherapy because they are literal poisons. Clinical trial experience in 1 field does not make you an expert in all research. Except perhaps in one’s mind.
He is actually criticized by nearly everyone. He tried to reject a mRNA flu vaccine over a dispute about whether to use he high dose variant in the over 65 group as a control. This issue was discussed before the trial and the methodology of the trial was approved by the FDA before it ran. The vaccine got a unanimous approval once his move to block it was overturned. Unanimous by the relatively vaccine skeptic Trump FDA panel - appointed by the current FDA commissioner. Prasad didn’t want it to even come to a vote because of a methodologic complaint in the study. And 9 votes to zero approved the vaccine.
Nearly everyone criticizes him.
And then there is Canada - published in a complete garbage journal - Lancet Neurology. Feb 2026.
Please note the comment about quality of journals is complete and utter sarcasm. These are both elite journals. Both arguably number 1 in their fields. Lancet is consistently ranked number 1 for Neurology and Annals is the most cited internal medicine specialty journal.
There’s no cherry picking. Vinay included both the JAMA and Annals paper in his video. His main criticisms appears to be the pre-test probability and time to dementia diagnosis, as well as the contradictory study based on data from England and Wales.
I certainly can’t watch that again but I did not recall that he mentioned all those studies - you said JAMA and I quoted Lancet but Annals matched. Maybe a transcript would be helpful? Maybe YouTube isn’t the place for real science? It caters to people who are too lazy to read. Any serious scientist sticks to publications but this requires peer review so you can’t put garbage in a publication as easily.
He knows more that the peer review of all the elite medical journals. And the consensus view from nearly every researcher on the topic.
We all know RCTs are the highest standard. Every other study technique has criticism - he likes to think he is so brilliant by pointing that out. He should stick to oncology.
There is significant evidence of a VZV and HSV coactivation as a cause of Alzheimer’s. And TBI activation of HSV. The HSV hypothesis dates to the 90s. It all falls on the inflammaging paradigm - in this case dormant viruses being the cause of the inflammation.
Varicella reactivation increases risk of CVD and stroke. The virus has been found in cerebral artery walls. A shingles infection known to increase the risk of dementia.
Given all we know about Varicella, it would actually be surprising if the vaccine didn’t reduce dementia rates.
I could probably post an article a day and never run out of references from elite journals.
They’re not comparable to RCT’s, they tell you about the rates of dementia diagnosis, but that might be different because people who get shingles encounter healthcare to receive a diagnosis. That’s why control groups are important that have similar rates of healthcare encounters. Why there was no effect in the larger England-Wales paper I’m not sure. You can also pick whatever tools you want to use which increases the risk of p-hacking.
Does it increase risk of CVD and stroke in studies with this design?
Here’s an older post where he critizes the Annals and JAMA paper, and a U.S one:
As well here’s the transcript of the relevant part from the video:
Confidence intervals cross one, so it Loses significance statistical Significance. But, what they don’t do is They can’t knock down the entire Magnitude of effect. Which suggests There may be some idiosyncratic Background noise in Wales that led to That false finding. Well, that’s not the only paper on the Topic. There are a whole bunch of other Papers on the topic, and in Vinay Prasad’s Observations and Thoughts, my Substack, I walk you through some of That other literature. Some of that other literature includes Papers in the Annals of Internal Medicine that shows that among nursing
Home residents who are hospitalized in a Nursing home or put into a home. I guess Technically not hospitalized, they are In a nursing home. Those who received a Shingles vaccine had a lower risk of Dementia than those who don’t. But the Finding that I find most notable is that The shot seems to work as soon as 200 Days. Within a year, it’s already Kicked in. Boy, this is the fastest Intervention for dementia you could ever Imagine. It works faster than Tums. Dementia is a long-standing process, Takes years, perhaps decades to come on
In full. And you have an intervention That can turn around so quick. Boy. What else do I note? There’s another Paper in JAMA, which looks at the Shingles vaccine. I’ll show the time to Event plots, the probability of dementia Among those eligible or ineligible for The shingles vaccine program. And boy, Again, boy, by the time a year is up, Maybe by 100 days, the shingles shot is Already halting dementia. Wow, so fast, So amazing. And let me show you one last Graph, which shows a near instant Reduction in the rate of dementia before And after a different cutoff in a
Different country. I believe this is a US data set from Nature Communications. And again, it works so quick. The Wales Paper never showed you how fast it Works. What’s my point here? My point Here is that in observational studies, If interventions work too quickly beyond What is biologically plausible, that Really smells a lot like selection bias. The final piece of evidence I’ll show That undermines the claim that shingles Vaccines reduce dementia is a Meta-analysis of observational studies Of all sorts of vaccines. This is Diphtheria, influenza, pertussis.
