A Vaccine for Dementia? The Evidence Is Astonishing.

Summary

Dr. Alex reviews whether shingles vaccination might also reduce or delay dementia. The evidence is promising but mixed, and it has not been proven that the vaccine prevents dementia.

Shingles is caused by the varicella-zoster virus, which remains dormant in nerve cells after chickenpox and can reactivate later in life. It can cause a painful, one-sided rash and lingering nerve pain. If it affects nerves near the eye, it can be particularly serious.

Researchers have suggested that repeated viral reactivation and inflammation could affect the brain, or that Shingrix’s immune-stimulating ingredient might have broader effects. Neither explanation has been established.

What the studies found

• Welsh study: A birth-date eligibility cutoff created a natural experiment. Among more than 280,000 older adults followed for seven years, vaccination was associated with about a 20% lower likelihood of a dementia diagnosis—roughly 17–18 diagnoses per 100 people versus around 14. The association was clearer in women than in men.
• Oxford study: Researchers comparing people who received the older vaccine with those who received Shingrix found that the newer vaccine was associated with 17% more time without a dementia diagnosis. Among people eventually diagnosed, the diagnosis came about 164 days later on average. This was observational research, so it cannot establish cause and effect.
• Large English study: Using a similar birth-date approach and hospital records for about 6.3 million people, researchers found no detectable reduction in dementia. The study was still a preprint, and hospital records may miss diagnoses made in primary care.
• Bottom line: The results conflict. Randomized trials in Finland and Denmark are underway, but their results will take years.

Practical health guidance

• Consider shingles vaccination primarily for its established protection against shingles, not as a proven dementia-prevention treatment. In trials, two doses of Shingrix prevented more than nine in ten shingles cases, including among people over 70.
• In the UK, the NHS offers vaccination to certain age groups and to some people with severely weakened immune systems. Check your eligibility with a GP or healthcare provider. In the US, the CDC recommends it for adults aged 50 and older, and it is usually covered by insurance.
• Vaccination may still be relevant if you have had shingles before, since shingles can recur. If you are considering paying privately, discuss the decision with your doctor and keep in mind that any brain-health benefit remains uncertain.
• Common short-term effects include arm pain, tiredness, aches, and a mild fever. Avoid the vaccine after a severe allergic reaction to a previous dose or an ingredient. Consult your doctor if you are immunocompromised or receiving chemotherapy.
• For brain health, focus on steps with stronger evidence:
  • Keep blood pressure under control.
  • Monitor hearing and use hearing aids if needed.
  • Don’t smoke.
  • Manage blood sugar and LDL cholesterol.
  • Move regularly and stay socially connected.
• Seek medical advice for memory or cognitive symptoms that are persistent, unusual, or severe.

Presenters and sources mentioned

• Presenter: Dr. Alex
• Other person mentioned: Steph, Dr. Alex’s wife and a doctor
• Sources and organizations: The Guardian; Boots; Superdrug; the Welsh shingles study published in Nature; Oxford researchers; the English study, described as a preprint; the Finland and Denmark randomized trials; the 2024 Lancet Commission on Dementia; Alzheimer’s Research UK; the NHS; and the US CDC.