December 3, 2020 – Could vaccines play a role in preventing Alzheimer’s disease?
Researchers are examining this question more broadly after finding that flu and pneumonia vaccines may also help protect against the devastating memory loss in Alzheimer’s disease.
Svetlana Ukraintseva, PhD, Associate Research Professor in the Biodemography of Aging Research Unit at the Social Science Research Institute at Duke University, investigated a possible link between the pneumonia vaccine and the disease of ‘Alzheimer’s in a study published this year.
She says her team is now studying the effects of vaccines on Alzheimer’s disease on a larger group – 50,000 people. She also plans to study whether other vaccines, beyond flu and pneumonia vaccines, might boost immunity and protect against Alzheimer’s disease, and how infections like pneumonia and herpes affect the risk of Alzheimer’s.
“So we can compare not only how several different vaccines affect Alzheimer’s disease, but also several different infectious diseases,” she says. She expects to have results in about a month and will then disclose which vaccines are being studied.
The pneumonia vaccine
The Ukraintseva study looked at data from more than 5,000 people, aged 65 and older, who were part of the Heart Health Study, sponsored by the National Heart, Lung, and Blood Institute. The authors found that getting a pneumonia vaccine between the ages of 65 and 75 reduced the risk of Alzheimer’s disease by up to 30%. In people who did not carry a specific genetic risk factor for Alzheimer’s disease – called rs2075650 G – the reduction in Alzheimer’s risk was even better – up to 40%.
Ukraintseva says she chose this particular genetic risk factor because it helps regulate the blood-brain barrier. This barrier prevents viruses and other harmful substances from entering the brain. A weakened barrier could contribute to Alzheimer’s disease.
The flu vaccine and Alzheimer’s disease
In another study from this year, people who received one or more flu shots were 17% less likely to get Alzheimer’s disease. Those who got the flu shot more often had a 13% lower additional risk. Getting the first flu shot earlier in life – at age 60 – seemed to offer better protection than waiting until age 70 to get the vaccine.
“Overall, we found that flu shots and more frequent flu shots were associated with fewer cases of Alzheimer’s disease,” says Albert Amran, a fourth year medical student at McGovern Medical School at UTHealth , who led the study.
These aren’t the only studies to link vaccines to a reduced risk of Alzheimer’s disease. An older study of 4,000 people aged 65 and over found that people who had been exposed to the diphtheria, tetanus, polio, or flu vaccine had a lower risk of dementia. In another study, people with chronic kidney disease who were vaccinated against the flu were 30 to 40% less likely to get dementia, compared to those who were not vaccinated.
How could vaccines protect against Alzheimer’s disease?
Researchers aren’t sure exactly, but they have a few theories. “Perhaps preventing the viral infection itself could protect [brain] complications from the infection, ”Amran says.
Another possibility concerns the immune system in general. As we age, our immune system weakens and it cannot respond as quickly or as strongly to viruses and other threats as when we were young. It is also not as effective in preventing harmful substances from entering our brain, nor as effective in repairing damage that occurs to the brain.
Vaccines not only prevent a specific type of infection, but they can also boost the immune system. “You have this immune response activated for maybe several months or years, which also allows you to be protected against a bunch of other diseases,” Ukraintseva says.
It is also possible that people who get vaccinated take better care of their health in other ways – for example, by eating a healthy diet and exercising – which may protect them from Alzheimer’s disease. The authors of the two studies tried to control other healthy practices, but could not confirm whether they played a role in the prevention of Alzheimer’s disease.
To take away
Recommended flu and pneumonia vaccines protect you against these infections and the complications they can cause. Both of these studies suggest that these vaccines may also offer an added benefit in protecting you against dementia.
Vaccines could also have another benefit. Because they stimulate the response of the immune system as a whole, they could help people live longer, says Ukraintseva. “The million dollar question is to select all the vaccines with this rejuvenating effect on the immune system. In this case, we will have two victories: preventing Alzheimer’s disease and possibly some kind of anti-aging intervention.”
The CDC recommends that anyone over 6 months old get a flu shot every fall, and that adults over 65 get a pneumococcal vaccine to protect against these infections.