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Routine Vaccines Associated With A Reduced Risk of Developing Alzheimer’s Disease

Great news! A recent study found that older adults who get routine vaccinations have a  lower risk of developing Alzheimer's disease and related dementias. Other studies looking at adults over the age of 60  and routine vaccinations (flu, pneumonia) have had similar findings.

The vaccinations that were looked at in this study were: the shingles (herpes zoster) vaccine, pneumococcal vaccine, and tetanus-diphtheria vaccine. Each of the vaccines lowered the risk of getting AD - the tetanus-diphtheria (Tdap/Td) by 30%, the shingles vaccine by 25%, and the pneumococcal vaccine by 27%. The adults were at least 65 years of age at the start of the study.

Why would vaccines be protective? There  are multiple theories, including that infection may play a role in the development of Alzheimer's disease (AD), and vaccines reduce the risk for infections. Or that vaccines may activate the immune system in such a way that alters the risk for developing AD.

Bottom line: In persons over the age of 60, getting routine adult vaccinations (including the flu vaccine) may lower the risk of developing AD. So simple!

From Medical Xpress: Several vaccines associated with reduced risk of Alzheimer's disease in adults 65 and older

Prior vaccination against tetanus and diphtheria, with or without pertussis (Tdap/Td); herpes zoster (HZ), better known as shingles; and pneumococcus are all associated with a reduced risk for developing Alzheimer's disease, according to new research from UTHealth Houston.

Alzheimer's disease affects more than 6 million people living in the U.S., with the number of affected individuals growing due to the nation's aging population.

The new findings come just over a year after Schulz's team published another study in the journal, which found that people who received at least one influenza vaccine were 40% less likely than their unvaccinated peers to develop Alzheimer's disease.

"We were wondering whether the influenza finding was specific to the flu vaccine. This data revealed that several additional adult vaccines were also associated with a reduction in the risk of Alzheimer's," said Schulz, who is the Umphrey Family Professor in Neurodegenerative Diseases and director of the Neurocognitive Disorders Center at McGovern Medical School. "We and others hypothesize that the immune system is responsible for causing brain cell dysfunction in Alzheimer's. The findings suggest to us that vaccination is having a more general effect on the immune system that is reducing the risk for developing Alzheimer's."

Researchers performed a retrospective cohort study that included patients who were free of dementia during a two-year lookback period and were at least 65 years old by the start of the eight-year follow-up period. They compared two similar groups of patients using propensity score matching, one vaccinated and another unvaccinated, with Tdap/Td, HZ, or pneumococcal vaccine. Ultimately, they calculated the relative risk and absolute risk reduction for developing Alzheimer's disease.

Patients who received the Tdap/Td vaccine were 30% less likely than their unvaccinated peers to develop Alzheimer's disease (7.2% of vaccinated patients versus 10.2% of unvaccinated patients developed the disease). Similarly, HZ vaccination was associated with a 25% reduced risk of developing Alzheimer's disease (8.1% of vaccinated patients versus 10.7% of unvaccinated patients). For the pneumococcal vaccine, there was an associated 27% reduced risk of developing the disease (7.92% of vaccinated patients versus 10.9% of unvaccinated patients).

"We hypothesize that the reduced risk of Alzheimer's disease associated with vaccines is likely due to a combination of mechanisms," Bukhbinder said. "Vaccines may change how the immune system responds to the build-up of toxic proteins that contribute to Alzheimer's disease, such as by enhancing the efficiency of immune cells at clearing the toxic proteins or by 'honing' the immune response to these proteins so that 'collateral damage' to nearby healthy brain cells is decreased. Of course, these vaccines protect against infections like shingles, which can contribute to neuroinflammation."

The Tdap vaccine protects against tetanus, diphtheria, and whooping cough, also known as pertussis, while the Td vaccine protects against the former two. Adults need a Td or Tdap booster shot every 10 years to keep a high level of protection against tetanus, which is commonly referred to as "lockjaw," and diphtheria, a serious bacterial infection that typically affects the mucous membranes of the nose and throat.

HZ protects against shingles, a reactivation of the chickenpox virus in the body that causes a painful rash. The Centers for Disease Control and Prevention (CDC) recommends adults 50 years and older, as well as adults 19 years and older who have or will have weakened immune systems because of disease or therapy, get two doses of the shingles vaccine called Shingrix.

Meanwhile, the pneumococcus vaccine protects against pneumonia, meningitis, sinus infection, blood infection, and middle ear infection. Pneumococcal disease is common in young children, but older adults are at greatest risk of serious illness and death; consequently, the CDC recommends pneumococcal vaccination for all children younger than 5 years old and all adults 65 and older.

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