Shingles Vaccine May Reduce Dementia Risk and Could Slow Disease Progression

It has long been suspected that the shingles vaccine impacts the development of dementia. However, strong evidence from clinical trials to confirm suspicions about the protective effects of the vaccine on the neurodegenerative disease was lacking.

Now, Stanford Medicine researchers report in Nature And Cell that people who received the shingles vaccine were about 20 percent less likely to develop dementia than those who did not receive it. The analysis, based on Welsh health records, also found that vaccinated people diagnosed with dementia were less likely to die from the disease, suggesting the shot may influence disease progression as well as risk.

Learn more: Why do painful shingles blisters appear in people under 50?

Why shingles might be important for dementia

The varicella-zoster virus, which causes chickenpox in children, remains dormant in the nervous system long after the initial infection has resolved. In old age, the virus can reactivate in the form of shingles, which can sometimes lead to serious neurological complications.

In recent years, researchers have increasingly explored the possibility that viruses affecting the nervous system may contribute to dementia risk. As millions of people worldwide suffer from dementia, identifying modifiable risk factors has become a public health priority.

According to the study’s press release, previous studies have reported associations between shingles vaccination and lower rates of dementia. However, these results carry great uncertainty:

“All of these association studies suffer from the fundamental problem that people who get vaccinated have different health behaviors than those who don’t,” said study lead author Pascal Geldsetzer, an assistant professor in the Division of Primary Care and Population Health at Stanford University, in the press release. “In general, they are not considered strong enough evidence to make recommendations.”

Unusual vaccination program provides strong data on dementia

A quirk of public health policy allowed the Stanford team to overcome this limitation.

In 2013, Wales faced a shortage of shingles vaccine and limited eligibility to those aged 79 by September 1 of that year – for one year only. Those who were already 80 years old were definitely excluded.

As a result, eligibility depended entirely on a narrow date of birth, not health status or personal choice, and the researchers were able to isolate the impact of the vaccination itself.

“Because of the unique way the vaccine was rolled out, bias in the analysis is much less likely than would usually be the case,” Geldsetzer said.

The study analyzed the records of more than 280,000 adults aged 71 to 88 who did not initially have dementia. Over seven years, vaccinated people experienced a 37 percent reduction in cases of shingles and a 20 percent reduction in the risk of dementia.

“What makes the study so powerful is that it is essentially like a randomized trial with a control group – those a little too old to be eligible for the vaccine – and an intervention group – those just young enough to be eligible,” he added. “It was a really striking finding. This huge protective signal was there no matter which way you looked at the data.”

Potential of shingles vaccine to slow progression of dementia

Additional analysis suggested benefits beyond delayed onset. Vaccinated people were less likely to be diagnosed with mild cognitive impairment, and those vaccinated after a dementia diagnosis were significantly less likely to die from the disease during nine years of follow-up.

“The most interesting thing is that this really suggests that the shingles vaccine not only has preventative and delaying benefits for dementia, but also therapeutic potential for those who already have dementia,” Geldsetzer said.

The biological mechanism remains unknown, although effects on the immune system or reduced viral reactivation are possible explanations. Geldsetzer and colleagues are now calling for a large randomized clinical trial to determine whether the relationship is causal.

This article does not offer medical advice and should be used for informational purposes only.

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