Vaccines help older people more than we knew

Let’s be clear. The main reason to get a shingles vaccine is that two shots provide 90 percent protection against a painful, blistering disease that a third of Americans will suffer from in their lifetime and that can cause persistent nerve pain and other dire long-term effects.

The most important reason for vaccinating older adults against the respiratory infection RSV is that their risk of being hospitalized with it decreases by almost 70 percent in the year of vaccination and by almost 60 percent in two years.

And the main reason for an annual flu vaccination is that it reliably reduces the severity of the illness if you become infected. However, effectiveness depends on how well scientists have predicted which flu strain will emerge.

But there are also other reasons for vaccinating older people. In medical jargon, they are known as “off-target benefits,” meaning that the vaccines have good effects beyond preventing the diseases they are intended to prevent.

The list of non-target benefits is growing as “research has increased and accelerated over the last 10 years,” Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center.

Some of these protections have been established through years of data collection; others are the subject of recent research and the benefits are not yet as clear. The RSV vaccine, for example, only became available in 2023.

Nevertheless, the results were “really very consistent,” said Dr. Stefania Maggi, geriatrician and senior fellow at the Institute of Neuroscience of the National Research Council in Padua, Italy.

She is the lead author of a recent meta-analysis published in the British journal Age and Aging, which found that the risk of dementia is reduced following vaccinations against a number of diseases. Given these “downstream impacts,” vaccines are “important tools to promote healthy aging and prevent physical and cognitive decline.”

But too many older adults, who are at higher risk of infectious diseases because of weaker immune systems and high rates of chronic disease, have not taken advantage of the vaccine.

The Centers for Disease Control and Prevention reported in mid-December that about 37 percent of older adults had not yet received a flu shot. Only 42 percent have ever been vaccinated against RSV, and less than a third received the latest Covid vaccination.

The CDC recommends a single pneumococcal vaccine for adults age 50 and older. But an analysis in the American Journal of Preventive Medicine estimated that from 2022, when new guidelines were issued, to 2024, only about 12 percent of those ages 67 to 74 received them, and about 8 percent of those 75 and older received them.

The strongest evidence of off-target benefits, dating back 25 years, shows reduced cardiovascular risk after flu shots.

Healthy older adults who are vaccinated against influenza have a significantly lower risk of being hospitalized for heart failure, pneumonia and other respiratory infections. Vaccination against influenza is also associated with a lower risk of heart attack and stroke.

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

Could the RSV vaccine, which protects against another respiratory disease, have similar cardiovascular effects? A recent large Danish study of older adults found a nearly 10 percent drop in cardiorespiratory hospitalizations – heart and lung – among those vaccinated compared to a control group, a significant decline.

However, lower rates of cardiovascular hospitalization and stroke did not reach statistical significance. This could be due to a short follow-up period or inadequate diagnostic testing, Dr. 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 influenza,” said Dr. Chu. “It’s just too early to have the information for RSV, but I think it will have the same effect, maybe even more.”

Vaccination against another dangerous respiratory disease, Covid-19, is associated with a lower risk of developing long-Covid, with its harmful effects on physical and mental health.

The most provocative findings concern the vaccination against shingles, also known as herpes zoster. Last year, researchers made headlines when they documented a link between the shingles vaccine and lower rates of dementia – even with the less effective vaccine, which 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, effective vaccine to a control group that could then become infected with the disease.

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

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

But Stanford researchers seized on 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. Whoever did it was ineligible.

Over seven years, dementia rates fell by 20 percent in participants who were eligible for vaccination – even though only half had actually been vaccinated – compared to those who narrowly missed the cutoff.

“There is no reason why people born a week earlier were different than those born a few days later,” said Dr. Maggi. Studies in Australia and the United States have also shown that the risk of dementia is reduced after a shingles vaccination.

In fact, in Dr. Maggi and her team published a meta-analysis of several other vaccinations for children and adults showing such effects. “We now know that many infections are associated with the onset of dementia, both in Alzheimer’s disease and vascular dementia,” she said.

In 21 studies involving more than 104 million participants in Europe, Asia and North America, the shingles vaccine was associated with a 24 percent reduction in the risk of dementia. The flu shot was associated with a 13 percent reduction. In people who were vaccinated against pneumococcal infection, the risk of Alzheimer’s disease was reduced by 36 percent.

Tdap vaccination against tetanus, diphtheria and pertussis (whooping cough) is recommended for adults every 10 years, although vaccination in older adults is often triggered by the birth of a grandchild who may not be fully vaccinated for months. This was associated with a reduction in dementia by a third.

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

What causes such vaccination premiums? Most hypotheses focus on the inflammation that occurs when the immune system mobilizes to fight off an infection. “You have damage to the environment” in the body, “and that takes time to calm down,” Dr. Chu.

The effects of inflammation can far outlast the initial illness. It can cause other infections to spread or cause heart attacks and strokes if blood clots form in narrowed blood vessels. “If you prevent the infection, you also prevent this other damage,” said Dr. Chu.

Hospitalization itself, during which older patients can become deconditioned or develop delirium, is a risk factor for dementia, among other health problems. Vaccines that reduce hospitalization could therefore delay or stave off cognitive decline.

Health officials in the Trump administration have attacked vaccinations for children more than for adults, but their vocal opposition could also contribute to the undervaccination of older Americans.

Not only will many miss out on emerging off-target benefits, but they will continue to be vulnerable to the diseases that the vaccines prevent or reduce.

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

The New Old Age is produced in collaboration with KFF Health News.