I wrote about shingles here in 2012. Back then the vaccine question was simple and slightly boring: there was one shot, it worked reasonably well, and most people over 60 were told to consider it.

The question I get now is different. People do not ask me whether the shingles vaccine prevents shingles. They ask whether it protects the brain.

That is a fair question, the evidence behind it is more interesting than most vaccine headlines, and it has a catch in it that almost nobody reporting on it mentions.

Start with the boring part, because it is the part that matters

Shingles is the chickenpox virus waking up. It sat in a nerve root for decades and then came back out along that nerve, which is why the rash arrives in a band on one side and stops at the midline.

The rash heals. The nerve pain is the problem. Postherpetic neuralgia is burning, electric pain in the same distribution that can outlast the rash by months, occasionally years, and it is genuinely difficult to treat once it settles in. That, not the rash, is the reason to care about this.

The current vaccine is Shingrix, given as two doses. In the ZOE-50 trial across more than 15,000 adults aged 50 and over, efficacy against shingles was 97.2 percent (1). In ZOE-70, in adults 70 and older, it was 89.8 percent, and in the pooled analysis of everyone over 70 across both trials, efficacy against postherpetic neuralgia specifically was 88.8 percent (2).

Those are very good numbers. Vaccines rarely perform like that in the age group where you most want them to work.

It is a reactogenic shot. Roughly one in six people feels properly unwell for a day or two after a dose, sore arm, tired, achy, sometimes feverish. I tell people that in advance, because a person who was warned takes the second dose and a person who was ambushed does not.

The dementia finding, and the catch

Here is where it gets interesting.

In 2025, a group at Stanford published a study in Nature that used an accident of Welsh policy (3). When Wales rolled out the shingles vaccine, eligibility was set by exact date of birth. Anyone born before 2 September 1933 was ineligible, permanently. Anyone born on or after that date was eligible.

Think about what that creates. A person born on 1 September 1933 and a person born on 3 September 1933 are, on average, identical in every way that matters. Same generation, same health, same everything. The only systematic difference between them is that one could get the vaccine and one could not. Uptake went from 0.01 percent in the group one week too old to 47.2 percent in the group one week younger.

That is as close to a randomized trial as you will ever get out of routine health records without running one.

Over seven years, the vaccinated group had a 3.5 percentage point lower probability of a new dementia diagnosis, which works out to a 20 percent relative reduction (3). The effect was stronger in women. The authors then reproduced it in a separate population using death certificates rather than diagnoses, which guards against the finding being an artifact of who happens to get diagnosed.

Now the catch.

Wales was using Zostavax, the old live-attenuated vaccine. That product was withdrawn from the US market in November 2020. It is not what you would be offered today, and the study does not tell you what Shingrix does.

A separate group looked at exactly that, using the rapid switchover from live to recombinant vaccine as its own natural experiment, and found the recombinant vaccine associated with a 17 percent increase in dementia-free time, about 164 extra days without a diagnosis among those who went on to be diagnosed, over six years (4). Again larger in women. I will note, because they note it, that the senior author consults for the manufacturer, and that GSK had no involvement in the study and did not know about it until after acceptance.

What I actually think about it

I think the signal is real and I do not think it should be the reason you get the shot.

Those are compatible positions. The dementia work is observational in design even when it is cleverly built, the mechanism is unproven, and no randomized trial has tested it. Something could still be wrong with it. Meanwhile the case for Shingrix rests on two large randomized controlled trials showing it prevents a disease that causes months of nerve pain, and that case was already sufficient on its own.

So my framing is this. Get it because postherpetic neuralgia is miserable and largely preventable. If the dementia finding holds up, you will have gotten that for free.

What the finding does change is urgency. I used to be relaxed when someone in their early fifties wanted to put it off a few years. I am less relaxed now, because if there is a neurological benefit it presumably accrues with time, and there is no advantage to waiting.

The part that belongs to my day job

Most of my practice is metabolic, and shingles turns out to sit closer to that than it looks.

A meta-analysis of sixteen studies put the risk of shingles in people with diabetes at a pooled relative risk of 1.38 compared with the general population (5). A separate population cohort found that people with diabetes had roughly 1.45 times the risk of postherpetic neuralgia, and that when they got it, it tended to be more severe and more persistent (6).

So the group most likely to get shingles, and most likely to be left with lasting nerve pain afterward, overlaps heavily with the group I see for weight and glucose.

There is a second reason this matters in diabetes that has nothing to do with the vaccine. Postherpetic neuralgia and diabetic peripheral neuropathy feel similar, they get treated with the same drugs, and I have seen the second diagnosis absorb the first. If burning pain shows up in a band, on one side, in a person who also has stocking-glove neuropathy, that is shingles until proven otherwise, whatever the chart already says.

Age 50 is also, not coincidentally, right in the middle of the menopause transition, which is the other half of what I do. If a woman is already in front of me talking about hormone therapy and bone density, the shingles vaccine is a reasonable thing to raise in the same visit, and often nobody has.

If you already have it, the clock is the thing

Antivirals for shingles work best started within 72 hours of the rash appearing. After that the benefit falls off steeply.

That single fact is the strongest argument I know for handling suspected shingles by video. A one-sided painful band of blistering rash with a burning prodrome is one of the more recognizable things in medicine, and a decent photograph plus a history usually settles it. The bottleneck has never been diagnostic difficulty. It has been how long it takes to be seen, and a visit you can get this afternoon beats a better visit on Thursday.

Two exceptions I do not manage remotely. A rash near or in the eye, particularly on the tip of the nose, needs same-day ophthalmology because of the risk to the cornea. Shingles in someone significantly immunocompromised, or a disseminated rash crossing the midline, goes in person.

For patients

If you are 50 or over, you are eligible for Shingrix regardless of whether you remember having chickenpox, and regardless of whether you had the old vaccine years ago.

If you are immunocompromised, the recommendation starts at 19 (7).

Expect to feel rough for a day after each dose, and get the second one anyway. One dose is not the regimen.

If a painful one-sided rash appears, get seen inside three days. Do not wait to see whether it spreads.

For colleagues

The dementia data is worth knowing and worth describing accurately. The strongest causal design was done on a product no longer sold in the United States, and patients who have read a headline usually have not been told that.

Diabetes belongs on the list of reasons to push the vaccine actively rather than mention it in passing.

And check the vaccine history of the metabolic patients. Nobody owns this conversation, so it tends not to happen. I have started treating it as part of the same visit rather than something to refer out, and it costs about ninety seconds.

The Bottom Line

Shingrix prevents shingles about 97 percent of the time in adults over 50, and it prevents postherpetic neuralgia, which is the thing actually worth avoiding. A natural experiment in Wales found 20 percent less dementia over seven years in vaccinated adults, and a second study suggests the current recombinant vaccine carries a similar signal, but the strongest of that evidence came from a live vaccine the United States no longer uses. Get the vaccine for the nerve pain it reliably prevents rather than the dementia it might. If you have diabetes, your risk of both shingles and lasting nerve pain afterward is meaningfully higher, which moves this up the list. And if a one-sided painful rash turns up, the antiviral window is 72 hours.

Related Reading

Shingles: “You Mean I Have Herpes?”

What Does Diabetes Do to Your Skin?

Newly Diagnosed With Type 2 Diabetes: What You Should Know

When to Use Telemedicine vs. Urgent Care: How I Spot the Sick One

Perimenopause and Menopause Symptoms and How to Manage Them

All About Cold Sores (Oral Herpes)

Scott Rennie, D.O.
Board Certified in Obesity Medicine and Family Medicine

This blog is for educational purposes only and does not constitute individual medical advice. Always consult your own physician before making changes to your health, medications, or treatment plan.

Sources

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2. Cunningham AL, Lal H, Kovac M, et al. Efficacy of the herpes zoster subunit vaccine in adults 70 years of age or older. N Engl J Med. 2016;375(11):1019-1032. PMID 27626517. https://pubmed.ncbi.nlm.nih.gov/27626517/

3. Eyting M, Xie M, Michalik F, et al. A natural experiment on the effect of herpes zoster vaccination on dementia. Nature. 2025;641(8062):438-446. PMID 40175543. https://pubmed.ncbi.nlm.nih.gov/40175543/

4. Taquet M, Dercon Q, Todd JA, Harrison PJ. The recombinant shingles vaccine is associated with lower risk of dementia. Nat Med. 2024;30(10):2777-2781. PMID 39053634. https://pubmed.ncbi.nlm.nih.gov/39053634/

5. Huang CT, Lee CY, Sung HY, et al. Association between diabetes mellitus and the risk of herpes zoster: a systematic review and meta-analysis. J Clin Endocrinol Metab. 2022;107(2):586-597. PMID 34536279. https://pubmed.ncbi.nlm.nih.gov/34536279/

6. Wen SY, Ou-Yang C, Hsu CY, et al. Impact of type 1 versus type 2 diabetes on developing herpes zoster and post-herpetic neuralgia: a population-based cohort study. Acta Derm Venereol. 2023;103:adv9400. PMID 37787418. https://pubmed.ncbi.nlm.nih.gov/37787418/

7. Anderson TC, Masters NB, Guo A, et al. Use of recombinant zoster vaccine in immunocompromised adults aged 19 years and older: recommendations of the Advisory Committee on Immunization Practices. MMWR Morb Mortal Wkly Rep. 2022;71(3):80-84. PMID 35051134. https://pubmed.ncbi.nlm.nih.gov/35051134/