Beyond prevention: Routine vaccines offer surprising health benefits for older adults

The list of unintended benefits is expanding as “research has accumulated and accelerated over the past 10 years,” said William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center in Nashville, Tennessee.

Some of these protections have been established by years of data; others are the subject of more recent research and the results are not yet so clear. The first RSV vaccines, for example, were not available until 2023.

Still, the findings “are actually very consistent,” said Stefania Maggi, a geriatrician and senior researcher at the National Research Council’s Neuroscience Institute in Padua, Italy.

She is the lead author of a recent meta-analysis, published in the British journal Age and Aging, that found a reduced risk of dementia after vaccination for a variety of diseases. Given those “after effects,” he said, vaccines “are key tools to promote healthy aging and prevent physical and cognitive decline.”

However, too many older adults, whose weakened immune systems and high rates of chronic diseases put them at higher risk for infectious diseases, have not taken advantage of vaccination.

The Centers for Disease Control and Prevention reported this month that about 31% of older adults had not yet received the flu vaccine. Only about 41% of adults aged 75 and older had ever been vaccinated against RSV, or respiratory syncytial virus, and about a third of older people had received the most recent COVID-19 vaccine.

The CDC recommends the one-time pneumococcal vaccine for adults age 50 and older. However, an analysis in the American Journal of Preventive Medicine estimated that from 2022, when new guidelines were issued, to 2024, only about 12% of people between 67 and 74 years old received them, and about 8% of those over 75 years old.

Flu and RSV Vaccines May Protect the Heart

The strongest evidence of unintended benefits, dating back 25 years, shows a reduction in cardiovascular risk after the flu vaccine.

Healthy older adults vaccinated against the flu have substantially lower risks of hospitalization for heart failure, as well as pneumonia and other respiratory infections. Flu vaccination has also been associated with lower risks of heart attack and stroke.

Additionally, many of these studies predate the more potent flu vaccines now recommended for older adults.

Could the RSV vaccine, protective against another respiratory disease, have similar cardiovascular effects? A recent large Danish study of older adults found a nearly 10% decrease in cardiorespiratory (involving the heart and lungs) hospitalizations among those vaccinated compared to the control group, a significant decrease.

“I don’t think RSV will behave any differently than the flu. It’s just too early to have any information on RSV, but I think it will show the same effect, maybe even more so.”

Helen Chu, infectious disease specialist

However, the reduced rates of cardiovascular hospitalizations and stroke did not reach statistical significance. That may reflect a short follow-up period or inadequate diagnostic testing, cautioned Helen Chu, an infectious disease specialist at the University of Washington and co-author of an accompanying editorial in JAMA.

“I don’t think RSV behaves any differently than the flu,” Chu said. “It’s too early to have information on RSV, but I think it will show the same effect, maybe even more.”

Vaccination against another dangerous respiratory disease, COVID, has been linked to a lower risk of developing long COVID, with its detrimental effects on physical and mental health.

Shingles Vaccine Shows Stronger Brain Link

Probably the most provocative findings concern vaccination against shingles, also known as shingles. Researchers made headlines last year when they documented an association between shingles vaccination and lower rates of dementia, even with the less effective vaccine that has since been replaced by Shingrix, approved in 2017.

Almost all studies of off-target benefits are observational, because scientists cannot ethically deny a safe and effective vaccine to a control group whose members could later become infected with the disease.

This means that such studies are subject to a “healthy volunteer bias,” because vaccinated patients can also practice other healthy habits, differentiating them from unvaccinated patients.

Although researchers try to control for a variety of potentially confounding differences, from age and sex to health and education, “we can only say that there is a strong association, not cause and effect,” Maggi said.

But Stanford researchers took advantage of a natural experiment in Wales in 2013, when the first shingles vaccine, Zostavax, became available to older people who were not yet 80 years old. Anyone who had it was ineligible.

Over seven years, dementia rates in participants who had been eligible for vaccination fell by 20% (although only half had received the vaccine) compared to those who narrowly missed the cutoff.

“There are no reasons why people born a week earlier would be different from those born a few days later,” Maggi said. Studies in Australia and the United States have also found reductions in the odds of dementia after the shingles vaccine.

In fact, in the meta-analysis Maggi and his team published, several other childhood and adult vaccines appeared to have these effects. “We now know that many infections are associated with the onset of dementia, both Alzheimer’s and vascular,” he said.

Studies show broad protective effects.

In 21 studies involving more than 104 million participants in Europe, Asia, and North America, shingles vaccination was associated with a 24% reduction in the risk of developing dementia. Flu vaccination was linked to a 13% reduction. Those vaccinated against pneumococcal disease had a 36% reduction in the risk of Alzheimer’s.

The Tdap vaccine for tetanus, diphtheria, and pertussis (whooping cough) is recommended for adults every 10 years, and vaccination among older adults is often triggered by the birth of a grandchild, who cannot receive the full vaccine for months. It was associated with a one-third decrease in dementia.

Other researchers are investigating the effects of the shingles vaccine on heart attacks and strokes and the COVID vaccine on cancer survival.

What causes such vaccine bonuses? Most hypotheses focus on inflammation that arises when the immune system is mobilized to fight an infection. “There is damage to the surrounding environment” in the body, “and that takes time to calm down,” Chu said.

The effects of inflammation can last much longer than the initial illness. It can allow other infections to take hold or cause heart attacks and strokes when clots form in narrowed blood vessels. “If you prevent infection, you prevent other damage,” Chu said.

Hospitalization itself, during which older patients may become deconditioned or develop delirium, is a risk factor for dementia, among other health problems. Therefore, vaccines that reduce hospitalization could delay or prevent cognitive decline.

Trump administration health officials have attacked childhood vaccines more than adult vaccines, but their outspoken opposition may also be contributing to inadequate vaccinations among older Americans.

Many will not only miss out on emerging off-target benefits, but will remain vulnerable to the diseases that vaccines prevent or diminish.

“Current national policy on vaccination is uncertain at best and, in some cases, appears anti-vaccine,” said Schaffner, a former member of the CDC’s Advisory Committee on Immunization Practices. “All of us who work in public health are very, very distressed.”

The New Old Age is produced through a partnership with The New York Times.

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This story originally appeared on KFF Health News.