The shingles vaccine helps prevent the reactivation of the virus that causes chickenpox. The chickenpox virus remains in the body after the initial infection and can later lead to shingles. (Image credit: Albany Times Union/Hearst Newspapers via Getty Images)
Compelling new evidence suggests that the shingles vaccine may reduce or delay the development of dementia.
In a study published April 23 in the journal JAMA, researchers analyzed electronic health records from across Australia. They found that older adults eligible for the free shingles vaccine were significantly less likely to be diagnosed with dementia over the next 7.4 years than those who were slightly older and not eligible for the vaccination program.
The findings support the “viral hypothesis” of Alzheimer's disease, which suggests that viral infections contribute to the condition, the most common form of dementia. In particular, the hypothesis focuses on herpesviruses, a group of viruses that includes the varicella-zoster virus, which causes both chickenpox and shingles.
If the new study's findings are confirmed by further research, it would mean there is an effective and inexpensive way to reduce the risk of developing dementia.
“It is difficult to imagine that anything other than the vaccine could explain the significant protective effect,” Dr. Sten Vermund, dean of the University of South Florida’s College of Public Health, who was not involved in the study, told Live Science in an email.
Pseudoclinical study
If a person contracts chickenpox, the varicella-zoster virus can remain dormant in the nervous system for decades before activating later, causing shingles, a condition characterized by a painful rash. The ability to remain latent and then “awaken” in the body is a key characteristic of herpes viruses.
The shingles vaccine helps build immunity and prevents the virus from becoming active again, making it very effective in preventing shingles and its complications, such as long-term neuralgia, vision loss, and increased risk of bacterial skin infections.
Previous studies have shown that older adults who get the shingles vaccine tend to have lower rates of dementia than those who don’t. However, these studies come with an important caveat: People who choose to get the vaccine also tend to be more health-conscious and more likely to eat a healthy diet and exercise regularly — habits that help protect against dementia. So while previous studies have shown an association between the shingles vaccine and a reduced risk of dementia, they have failed to prove a cause-and-effect relationship.
The gold standard for testing whether a vaccine actually protects against dementia would be to conduct a large clinical trial in which participants are randomly assigned to receive the vaccine or a placebo. However, such trials are expensive and may raise ethical questions.
“It would be useful to see a randomized controlled trial comparing placebo with the herpes vaccine, rather than a retrospective observational study like this one,” said Dr. Logan DuBose, co-founder of Olera.care, a support platform for people who care for the elderly. “However, there may be some ethical concerns about giving the vaccine to some people and not others” — given that it’s known to be effective against shingles — “which makes it difficult to conduct such a study,” DuBose, who was not involved in the work, added in an email to Live Science.
The new study took an alternative approach. “What’s special about our study is that we use a scenario that is very similar to a randomized trial,” senior author Dr. Pascal Geldsetzer, an assistant professor of medicine at St.
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