Shingles vaccine and dementia

Take the shingles vaccine when you are offered it, because it prevents shingles. Treat any protection against dementia as a possible bonus, not a reason on its own.

What it is

The shingles (herpes-zoster) vaccine protects against shingles. There are two kinds: the older live vaccine, and the now-standard recombinant vaccine (Shingrix). Almost all of the strongest dementia evidence concerns the older live one.

The birthdate experiments

Wales came first. A birthdate cut-off made the vaccine abruptly available to people born on or after 2 September 1933 but not to those born a week earlier. Over seven years, new dementia diagnoses among people who received the vaccine fell by 3.5 percentage points in absolute terms, a one-fifth relative reduction.^[1] People born a week apart differ in little but their eligibility, so the design mimics randomisation and sidesteps the "healthy-vaccinee" bias of ordinary observational studies, where the people who choose to get vaccinated tend to be healthier to begin with.

Australia and Canada pointed the same way. Similar birthdate natural experiments found that eligibility lowered new dementia diagnoses by about 2 percentage points over five and a half to seven and a half years.^[2][3]

A follow-up in Wales found fewer diagnoses of mild cognitive impairment, and fewer deaths from dementia among people already diagnosed.^[4]

Why the size is disputed

There is a serious objection. Few of the eligible people actually got vaccinated, so a drop measured across everyone eligible implies a much larger effect in those who were. Once that is accounted for, the Australian and Canadian results imply implausibly large effects in the vaccinated: in two of the three analyses (one Australian, two Canadian), more than 100% of their dementia prevented, which is impossible. National dementia rates also did not visibly fall after the vaccination programmes started.^[5]

So the evidence probably supports the claim that vaccination lowers dementia diagnoses, but it is weak on how large that effect is.

The newer vaccine

All of the birthdate experiments concern the older live vaccine. For the now-standard recombinant vaccine the evidence is observational only:

• Recipients had about 17% more dementia-free time than people given the live vaccine.^[6]
• Among about 510,000 US Medicare beneficiaries aged 66 or older admitted to a skilled-nursing facility, four-year dementia risk was 18.8% with the vaccine against 24.6% without, about a quarter lower. The manufacturer funded that study, and its own checks suggest some residual confounding.^[7]

What hasn't been tested

There is no randomised trial of either vaccine with dementia as the outcome. The birthdate studies are the closest thing, and they all concern the older live vaccine, in Wales, Australia and Canada.

What to do

1. Get vaccinated when you become eligible. The vaccine is recommended anyway to prevent shingles, so the dementia question does not change the decision.
2. Don't count on it as dementia prevention. The better-established levers, from blood pressure to hearing, are on Dementia prevention.

Further reading

• Eyting M et al. A natural experiment on the effect of herpes zoster vaccination on dementia. Nature 2025.^[8]
• Pomirchy M et al. Herpes Zoster Vaccination and Dementia Occurrence. JAMA 2025.^[9]
• Pomirchy M et al. Herpes zoster vaccination and incident dementia in Canada: an analysis of natural experiments. Lancet Neurol 2026.^[10]
• Kivimäki M et al. Natural experiments of herpes zoster vaccination: Quantifying the implied vaccine effectiveness against dementia. Brain Behav Immun 2026.^[11]
• Taquet M et al. The recombinant shingles vaccine is associated with lower risk of dementia. Nat Med 2024.^[12]