Shingles (Herpes Zoster) is a disease caused by the same virus (varicella-zoster) that produces chickenpox, but for those who have experienced this common childhood disease, the offending virus stays hidden in the body, typically remaining dormant in nerve cells for decades. As people age and their immune systems weaken, the virus can reactivate and cause shingles, a disease that attacks the distribution of a single nerve, which produces a painful, blistering rash that can persist for a lengthy period—weeks to months—and can be quite disabling.
Fortunately, we now have a highly effective vaccine (Shingrix) that can prevent this disease in later life. For this reason, I would recommend this vaccination in all those eligible over the age of 50, even in those who have never knowingly experienced chickenpox as a child.
But now, incentives to receive this form of prevention have risen because getting vaccinated against shingles can reduce the risk of developing dementia, according to the results of a large new study. This provides some of the strongest evidence yet that some viral infections can have effects on brain function years later and that preventing them can help stave off cognitive decline. The study, published recently in the journal Nature, found that people who received the shingles vaccine were 20 percent less likely to develop dementia in the seven years afterward, compared with those who were not vaccinated, a finding that is quite important, given that we don’t really have much else at this time that slows down the onset of dementia. Whether the protection can last beyond seven years can only be determined with further research. But with few currently effective treatments or preventions, shingles vaccines appear to have some of the strongest potential protective effects against dementia that we know of.
In the United States, about one in three people develop at least one case of shingles in their lifetime, the Centers for Disease Control (CDC) estimates. About a third of eligible adults have received the vaccine in recent years, according to the C.D.C. Several previous studies have also suggested that shingles vaccinations might reduce dementia risk, but most could not exclude the possibility that people who get vaccinated might have other dementia-protective characteristics, like healthier lifestyles, better diets or more years of education. But the new study ruled out many of those factors, strengthening the evidence of true efficacy.
Researchers tracked health records of about 280,000 people who were aged 71 to 88 and without dementia when the rollout began. Over seven years, nearly half of those eligible for the vaccine received it, while only a tiny number from the ineligible group were vaccinated, providing a clear before-and-after distinction.
To limit the likelihood of differences between the groups, researchers used statistical analyses to weigh data from those who turned 80 within a one-week period. They also looked for possible differences between the vaccinated and unvaccinated, assessing whether unvaccinated people received more diagnoses of dementia simply because they visited doctors more frequently, and whether they took more medications that could increase dementia risk, seeking almost 200 medications that have been shown to be at least associated with elevated Alzheimer’s risk. All these potentially complicating variables were eliminated.
The study involved an older form of shingles vaccine, Zostavax, which contains a modified version of the live virus. It has since been discontinued in the United States and some other countries because its protection against shingles wanes over time. The new vaccine, Shingrix, which contains an inactivated portion of the virus, is more effective and lasting, research shows.
Shingrix may be more protective against dementia than the older vaccine. Based on another “natural experiment,” the 2017 shift in the United States from Zostavax to Shingrix, it found that over six years, people who had received the new vaccine had fewer dementia diagnoses than those who got the old one. Of the people diagnosed with dementia, those who received the new vaccine had nearly six months more time before developing the condition than people who received the old vaccine.
There are different theories about why shingles vaccines might protect against dementia. One possibility is that by preventing shingles, vaccines reduce the neuroinflammation caused by reactivation of the virus, Inflammation is a bad thing for many chronic diseases, including dementia, so reducing these reactivations and the accompanying inflammation may have benefits for dementia. Both the new study and the Shingrix study provide support for that theory.
Another possibility is that the vaccines rev up the immune system more broadly. The new study offers some evidence for that theory too. It found that women, who have more reactive immune systems and larger antibody responses to vaccination than men, experienced greater protection against dementia than men. The vaccine also had a bigger protective effect against dementia among people with autoimmune conditions and allergies.
The study did not distinguish between types of dementia, but other research suggests that the effect of the shingles vaccine for Alzheimer’s disease is much more pronounced than for other dementias, which might be because some Alzheimer’s cases are associated with compromised immunity.
CONCLUSION
This information provides cogent reasons for all people to consider Shingrix as they age!
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