Could the shingles vaccine prevent or delay new-onset dementia? Ontario-based study suggests so

Health Canada recommends two doses of the shingles vaccine for adults who are over age 50 without contraindications. (Getty Images via CNN Newsource)

A new Ontario-based study is suggesting the shingles vaccine may help prevent and/or delay the onset of dementia more effectively than any existing treatment.

The study was published in Lancet Neurology and led by researchers at McMaster University and Stanford University. It analyzed health data from more than 250,000 seniors in Ontario and found the herpes zoster vaccination, also known as the shingles vaccine, helped significantly prevent dementia.

“There’s no pharmacological tool that has been shown to have such a large preventative effect,” Pascal Geldsetzer, lead researcher and Stanford University professor, told CTV News Toronto.

The study is rooted in Ontario’s shingles vaccine program introduced in September 2016. When Ontario first introduced the program, people who had their 71st birthday after Jan. 1, 2017, were eligible for the free vaccine whereas people who had their 71st birthday before this date were not – naturally creating two groups of people born immediately on either side of the cutoff date.

The study, which looked at data over a 5.5-year period for the two groups, found that the cohort that was eligible for the free vaccine based on their age had a lower probability of receiving a new dementia diagnosis by an absolute difference of two per cent compared to the group who was ineligible for the vaccine at the time.

Geldsetzer said that the difference worked out to about two fewer dementia cases per 100 people over the 5.5 years, which is a larger effect than existing dementia treatment can typically achieve.

“Shingles vaccination could be an effective preventative tool for dementia, which would have big implications because we have so little in the way of preventing and treating dementia,” Geldsetzer said. “Here, we would have a simple one-off, inexpensive, safe intervention.”

Geldsetzer said the research also found that after Ontario’s vaccine program started, new dementia diagnoses among the birth cohorts eligible for the vaccine were significantly less common than in the same birth cohorts in other Canadian provinces that did not have a similar program.

The Ontario-based study is now part of a body of research that has taken place in other regions of the world like the U.K. and Australia, and together are paving the way for a controlled, cause-and-effect study to cement the findings.

Geldsetzer added there’s evidence from the studies that the vaccine could even have benefits for people living with dementia.

“Our studies suggest that getting it before you develop any mild cognitive impairment has benefits, but that also getting it at later stages in dementia can also have benefits,” he said. “It really seems to have benefits for the dementia disease process across the whole spectrum.”

“We see large reduction in the probability of dying from dementia among those who already have dementia at the time of vaccination.”

It’s not clear exactly how Alzheimer’s and other types of dementia form, but the immune system is believed to be crucial in the development, he said. Certain viruses that make their way inside the nervous system have been suspected of adding to genetic and other factors that make people more vulnerable.

The exact reason why the shingles vaccine could help with dementia needs to be the subject of further research, Geldsetzer said, but he added that the vaccine may have a broader effect on the body’s immune response beyond what it has been designed to do.

Two years ago, doctors at Boston’s Brigham and Women’s Hospital reported that an episode of shingles could raise someone’s risk of dementia by about 20 per cent.

Stephenson Strobel, a McMaster University professor and an author of the study, told CTV News Toronto that their finding that the vaccine doesn’t just prevent the direct disease it is made for is significant.

“They may have this anti-inflammatory impact that not just directly impacts the disease itself but can kind of have a knock on effect that is especially important,” he said.

Dr. Roger Wong, a board member and chair of the research and knowledge transfer exchange committee with the Alzheimer Society of Canada, told CTV News Toronto on Friday that he feels excited about the new research because of the impact it would have on people living with dementia in the country.

“We have about 700,000 Canadians from coast to coast living with dementia and that number is on the rise. If nothing were to change by 2050, that number would hit three times more to about to about 1.8 million people,” he said.

This is the first study in Canada to show the positive impact of the shingles vaccine on dementia, he said, adding that it paves the way for a more controlled investigation.

“The design of the study is such that it is a big database study,” he said. “While it is not for sure causative in terms of the association, it does really pave the way for further research for us to have a better understanding of whether this is indeed true.”

“It really does provide a signal and a strong likelihood for us to do further research to explain whether it is truly a causative effect. This study is providing a strong association, not a cause and effort, but a strong possibility and probability.”

The study comes as researchers find that that over the next 30 years the number of people living with dementia in Canada is expected to increase by 187 per cent.

Geldsetzer said a more controlled study is next on his list and he is now fundraising to conduct further research.

“What is really needed now is a true randomized clinical trial on shingles vaccination for dementia prevention and that currently what I am focusing on,” he said.

The vaccine is currently free for Ontario adults aged 65 to 70 and is available as a two-dose series through primary care providers.