Most of us had chickenpox as children. Chickenpox is caused by a virus called the varicella virus. Varicella sticks around in our body even after our rashes and symptoms have faded. For most of our lives, the virus stays dormant and doesn’t cause any symptoms. But as we get older, it becomes more and more likely that the virus will reactivate. When it does, it causes shingles, a painful rash that is often accompanied by headache, chills, and nausea. It can also result in complications like postherpetic neuralgia (PNH), which is nerve pain that persists after the rash has subsided, as well as other serious conditions like vision or hearing loss or brain swelling [1]. Shingles is common; about one in three people in the United States will develop shingles in their lifetime, and that risk increases with age.
Luckily, there’s also a very effective way to prevent shingles: vaccination. Before 2020, a vaccine called Zostavax was available in the US. In 2020 a newer vaccine called Shingrix became available. Shingrix is recommended for people 50 years or older. It is 97% effective at preventing shingles in adults 50 to 69 years of age, and 91% effective in adults over 70. Shingrix is approximately 90% effective at preventing PNH in adults of all ages. Shingrix can also help prevent shingles in adults with weakened immune systems [1].
The two-dose Shingrix schedule is clearly effective at preventing shingles and complications of shingles. But recent studies have suggested that vaccination against shingles may also have other benefits.
A recent study used medical records from approximately 280,000 people in Wales to assess the incidence of dementia in those who did and didn’t receive a shingles vaccine. Typically, studies that compare people who get a vaccine to those who did not get a vaccine have an inherent bias: people who did not receive a vaccine may have other health risks that may be related to health issues, such as lack of access to medical care, thus making it impossible to determine cause versus effect. But Wales had a unique situation that allowed researchers to partially overcome this issue. When Wales rolled out the shingles vaccine, they had a particular eligibility structure. Anyone born on or before September 1, 1933 would not be eligible for the vaccine at any point, whereas anyone born on September 2, 1933 or later would be able to receive the vaccine. This eligibility policy was based on a variety of medical factors, but it had the unintended consequence of creating a natural randomized controlled trial, where researchers could compare two groups of people who were very similar except that some could get the vaccine and some could not.
When the researchers compared the dementia rates of those born before and after the eligibility date, they found that there was an 8.5% relative reduction in dementia diagnosis in those who were eligible for the vaccine, which was statistically significant. When they adjusted their analyses to account for vaccine uptake, as not all eligible individuals received the vaccine, they found that getting the vaccine was associated with an almost 20% relative reduction in dementia incidence (Pre-print) [2]. They found that the effect was particularly strong in women. While this study is not yet peer-reviewed, other studies have found similar associations between receipt of shingles vaccine and lower incidence of dementia [3; 4].
Interestingly, studies have also found associations between receipt of other vaccines and lower incidence of dementia [3; 4].These associations may not actually be related to the vaccines themselves. For instance, someone who gets vaccines may get more preventative care or have better access to medical care, which might be the real reason they have a lower incidence of dementia. However, it’s also possible that there is also a general protective effect of vaccines. For instance, vaccines may be able to modulate the immune system, reducing overall inflammation and providing ‘training’ to the immune system.
It is also possible that there is a specific protective effect of the shingles vaccine. The virus that causes shingles and chickenpox is present in nerve cells and can cause inflammation that could contribute to neurodegeneration. Some studies have also found that getting shingles is associated with a higher risk of a cardiovascular event like heart attack and stroke, and that people who get the shingles vaccine may have some protection against that risk [5; 6; 7].
Getting some protection against a painful condition like shingles is already a great benefit of a vaccine, and these studies show there may be other additional benefits. Like any medical intervention, there are always benefits and risks to weigh; talking to your doctor about whether the shingles vaccine is right for you is a good step towards better body and brain health.
Kathryn Carnazza, PhD, is a member of the ADDF's Aging and Alzheimer's Prevention program. She critically evaluates the scientific evidence regarding prospective therapies to promote brain health and/or prevent Alzheimer's disease, and contributes to CognitiveVitality.org. Dr. Carnazza earned a doctorate in neuroscience at Weill Cornell Graduate School of Medical Sciences, where she studied the molecular mechanisms of Parkinson’s disease. She also founded and organized a graduate school course on neurodegeneration at Weill Cornell. Dr. Carnazza obtained her bachelor's degree in biology from Tufts University.
Get the latest brain health news:
Can Herpesvirus Increase Your Risk for Alzheimer's Disease?
Can the flu vaccine protect against dementia?
Is There a Link Between Alzheimer's Disease and the Flu Shot?
Do infections accelerate cognitive decline?
Is there a link between the immune system and cognitive health?
Can COVID-19 cause long-term cognitive deficits?
Can COVID-19 accelerate brain aging?