At a time, when many are looking at certain vaccines with skepticism, especially the MMR vaccine and its alleged link (debunked by scientists) with autism, a new study revealed that the shingles vaccine may have some added benefits. Researchers at Stanford Medicine have found the strongest evidence yet that the shingles vaccine can lower the risk of dementia.
The remarkable study published in Nature, reveals that older adults who received the shingles vaccine were 20% less likely to develop dementia over the next seven years than those who did not.
What is shingles?
Shingles, also known as herpes zoster, is a viral infection caused by the varicella-zoster virus (VZV), the same virus that causes chickenpox. It causes a painful rash.
After a person contracts chickenpox, usually in childhood, the virus remains inactive in the nerve cells for life. When this virus reactivates, often when the immune system is weakened, shingles occur. According to the CDC, an estimated 1 million people get shingles each year in the US.
What is dementia?
Dementia is a term for several diseases that affect memory, thinking, and the ability to perform daily activities. Dementia affects over 55 million people worldwide, with an estimated 10 million new cases every year. The research around dementia has largely focused on the accumulation of plaques and tangles in the brains of people with Alzheimer’s, the most common form of dementia. However, with no breakthroughs in prevention or treatment, some researchers are exploring other avenues including the role of certain viral infections.
The new study’s results suggest that preventing shingles could have long-term neurological benefits. Though previous studies have linked the shingles vaccine with lower dementia rates, they could not account for a major source of bias: they couldn’t rule out a major bias: people who get vaccinated are often more health-conscious in ways that are hard to measure. Behaviors such as diet and exercise, for instance, are known to influence dementia rates, but are not included in health records.
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“All these associational studies suffer from the basic problem that people who get vaccinated have different health behaviors than those who don’t,” Pascal Geldsetzer, MD, PhD, assistant professor of medicine and senior author of the new study said in a statement. “In general, they’re seen as not being solid enough evidence to make any recommendations on.”
A natural experiment
Geldsetzer and his team identified an unusual ‘natural experiment’ in the rollout of the shingles vaccine in Wales that allowed them to sidestep the usual biases in observational studies. Beginning Sept. 1, 2013, the Welsh government made the vaccine available only to individuals who were exactly 79 years old. Those who had already turned 80 were permanently ineligible. And those who are 78 could wait an year, and get it.
By comparing people who just made the age cut-off with those who narrowly missed it, researchers could isolate the effect of the vaccine. They went through the health records of more than 280,000 older adults aged between 71 to 88 and did not have dementia at the start of the vaccination program.
“We know that if you take a thousand people at random born in one week and a thousand people at random born a week later, there shouldn’t be anything different about them on average,” Geldsetzer said. “They are similar to each other apart from this tiny difference in age.”
“What makes the study so powerful is that it’s essentially like a randomized trial with a control group, those a little bit too old to be eligible for the vaccine, and an intervention group, those just young enough to be eligible,” Geldsetzer said.
By 2020, one in eight older adults, who were by then 86 and 87, had been diagnosed with dementia. However, those who received the shingles vaccine were 20% less likely to develop dementia than the unvaccinated.
“It was a really striking finding. This huge protective signal was there, any which way you looked at the data,” Geldsetzer said.
Women had a better response
The researchers also found that the protection against dementia was much more pronounced in women than in men. This could be due to sex differences in immune response or in the way dementia develops, Geldsetzer said. Women on average have higher antibody responses to vaccination, for example, and shingles is more common in women than in men.
However, the researchers are yet to find out if the vaccine protects against dementia by revving up the immune system overall, by specifically reducing reactivations of the virus, or by some other mechanism.
As the study offers compelling evidence, researchers say the gold standard for proving cause and effect is a randomized controlled trial. Geldsetzer is now seeking funding for such a trial, where participants would be randomly assigned to receive either the shingles vaccine or a placebo shot.
“It would be a very simple, pragmatic trial because we have a one-off intervention that we know is safe,” he said.
If confirmed, the findings could provide an accessible and effective strategy for reducing dementia risk worldwide.
The remarkable study published in Nature, reveals that older adults who received the shingles vaccine were 20% less likely to develop dementia over the next seven years than those who did not.
What is shingles?
Shingles, also known as herpes zoster, is a viral infection caused by the varicella-zoster virus (VZV), the same virus that causes chickenpox. It causes a painful rash.
After a person contracts chickenpox, usually in childhood, the virus remains inactive in the nerve cells for life. When this virus reactivates, often when the immune system is weakened, shingles occur. According to the CDC, an estimated 1 million people get shingles each year in the US.
What is dementia?
Dementia is a term for several diseases that affect memory, thinking, and the ability to perform daily activities. Dementia affects over 55 million people worldwide, with an estimated 10 million new cases every year. The research around dementia has largely focused on the accumulation of plaques and tangles in the brains of people with Alzheimer’s, the most common form of dementia. However, with no breakthroughs in prevention or treatment, some researchers are exploring other avenues including the role of certain viral infections.
The new study’s results suggest that preventing shingles could have long-term neurological benefits. Though previous studies have linked the shingles vaccine with lower dementia rates, they could not account for a major source of bias: they couldn’t rule out a major bias: people who get vaccinated are often more health-conscious in ways that are hard to measure. Behaviors such as diet and exercise, for instance, are known to influence dementia rates, but are not included in health records.
Video
“All these associational studies suffer from the basic problem that people who get vaccinated have different health behaviors than those who don’t,” Pascal Geldsetzer, MD, PhD, assistant professor of medicine and senior author of the new study said in a statement. “In general, they’re seen as not being solid enough evidence to make any recommendations on.”
A natural experiment
Geldsetzer and his team identified an unusual ‘natural experiment’ in the rollout of the shingles vaccine in Wales that allowed them to sidestep the usual biases in observational studies. Beginning Sept. 1, 2013, the Welsh government made the vaccine available only to individuals who were exactly 79 years old. Those who had already turned 80 were permanently ineligible. And those who are 78 could wait an year, and get it.
By comparing people who just made the age cut-off with those who narrowly missed it, researchers could isolate the effect of the vaccine. They went through the health records of more than 280,000 older adults aged between 71 to 88 and did not have dementia at the start of the vaccination program.
“We know that if you take a thousand people at random born in one week and a thousand people at random born a week later, there shouldn’t be anything different about them on average,” Geldsetzer said. “They are similar to each other apart from this tiny difference in age.”
“What makes the study so powerful is that it’s essentially like a randomized trial with a control group, those a little bit too old to be eligible for the vaccine, and an intervention group, those just young enough to be eligible,” Geldsetzer said.
By 2020, one in eight older adults, who were by then 86 and 87, had been diagnosed with dementia. However, those who received the shingles vaccine were 20% less likely to develop dementia than the unvaccinated.
“It was a really striking finding. This huge protective signal was there, any which way you looked at the data,” Geldsetzer said.
Women had a better response
The researchers also found that the protection against dementia was much more pronounced in women than in men. This could be due to sex differences in immune response or in the way dementia develops, Geldsetzer said. Women on average have higher antibody responses to vaccination, for example, and shingles is more common in women than in men.
However, the researchers are yet to find out if the vaccine protects against dementia by revving up the immune system overall, by specifically reducing reactivations of the virus, or by some other mechanism.
As the study offers compelling evidence, researchers say the gold standard for proving cause and effect is a randomized controlled trial. Geldsetzer is now seeking funding for such a trial, where participants would be randomly assigned to receive either the shingles vaccine or a placebo shot.
“It would be a very simple, pragmatic trial because we have a one-off intervention that we know is safe,” he said.
If confirmed, the findings could provide an accessible and effective strategy for reducing dementia risk worldwide.
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