"Vaccines offer more than just protection against specific diseases; emerging research reveals a spectrum of ‘indirect benefits’ that significantly contribute to healthier aging, including reduced risks of cognitive decline and cardiovascular events."
The landscape of vaccination for older adults is expanding beyond its primary purpose of preventing targeted infectious diseases. Recent scientific inquiry is uncovering a compelling array of "indirect benefits"—positive health outcomes that extend beyond the immediate protection offered by vaccines like those for shingles, RSV, and influenza. These secondary advantages are increasingly supported by robust data, suggesting that vaccinations are powerful tools for promoting overall well-being and mitigating age-related health challenges.
For decades, the primary impetus for vaccination has been the direct prevention of serious illness. The shingles vaccine, for instance, offers a remarkable 90% protection against a painful and potentially debilitating condition that affects a third of all Americans. Similarly, the respiratory syncytial virus (RSV) vaccine significantly reduces the risk of hospitalization for older adults, with protection levels around 70% in the first year and a sustained 60% in the subsequent two years. The annual flu shot, while variable in efficacy depending on strain prediction, consistently lowers the severity of illness.
However, a growing body of evidence, accelerated in the last decade, points to a more expansive role for vaccines. As Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center, notes, "research has been accumulating and has accelerated in the last 10 years." These indirect benefits, while sometimes supported by decades of data, are also emerging from more recent studies, particularly with newer vaccines like the one for RSV, which became available in 2023.
Dr. Stefania Maggi, a geriatrician and senior researcher at Italy’s National Research Council Neuroscience Institute, highlights the consistency of these findings. She is the lead author of a significant analysis published in Age and Ageing, which examined multiple studies and found a reduced risk of dementia following vaccinations against various diseases. "Given these kinds of ‘chain reaction’ effects, vaccines are key tools for promoting healthy aging and preventing physical and cognitive decline," Dr. Maggi stated.
Despite the accumulating evidence of these broader health advantages, a significant portion of the older adult population remains under-vaccinated. This is particularly concerning given that the aging immune system is naturally more vulnerable, and the prevalence of chronic conditions further increases the risk of infectious diseases. As of mid-December, the Centers for Disease Control and Prevention (CDC) reported that approximately 37% of older adults had not yet received their annual flu shot. Vaccination rates for RSV were even lower, with only 42% having received the vaccine at least once. Furthermore, less than a third of this demographic had received the most recent COVID-19 vaccine.
The uptake of other recommended vaccines also lags. The CDC advises a single dose of the pneumococcal vaccine for adults aged 50 and older. However, an analysis in the American Journal of Preventive Medicine estimated that from 2022 to 2024, only 12% of individuals aged 67-74 and a mere 8% of those over 75 received the vaccine, even after updated recommendations.
The most robust and long-standing evidence for indirect benefits comes from studies on the influenza vaccine, spanning 25 years. These studies consistently demonstrate a reduction in cardiovascular risk following flu vaccination. Healthy older adults who get their flu shot exhibit a considerably lower risk of hospitalization for heart failure, as well as for pneumonia and other respiratory infections. Furthermore, flu vaccination has been linked to a decreased risk of heart attack and stroke. It’s important to note that many of these studies predated the availability of newer, more potent flu vaccines specifically recommended for older adults, suggesting that current vaccines may offer even greater protection.
The question naturally arises: could vaccines targeting other respiratory illnesses, such as RSV, offer similar cardiovascular benefits? A large-scale study conducted in Denmark among older adults provided intriguing insights. Researchers found a nearly 10% reduction in cardiorespiratory hospitalizations (involving both the heart and lungs) among vaccinated individuals compared to a control group—a significant decrease. However, the observed reduction in hospitalizations for cardiovascular diseases and strokes was not statistically significant. Dr. Helen Chu, an infectious disease specialist at the University of Washington and co-author of an accompanying editorial in JAMA, suggests this might be due to a short follow-up period or limitations in diagnostic testing. Nevertheless, she posits, "I don’t think RSV behaves very differently from the flu," anticipating similar, if not greater, cardiovascular benefits from the RSV vaccine as more data emerges.
The protection offered by COVID-19 vaccination also extends beyond preventing acute illness. Vaccination against COVID-19 has been associated with a reduced risk of developing "long COVID," a condition with far-reaching physical and mental health consequences.
Perhaps the most provocative findings emerge from research on the shingles vaccine. Last year, studies indicated an association between this vaccine and lower rates of dementia. This association was observed even with the older, less effective version of the vaccine, which has since been superseded by Shingrix, approved in 2017.
It is crucial to acknowledge that most studies on indirect benefits are observational. Ethical considerations prevent researchers from withholding safe and effective vaccines from control groups, which could lead to preventable illness. This methodological constraint means that findings may be influenced by "healthy volunteer bias," where vaccinated individuals may also engage in other healthy behaviors that differentiate them from unvaccinated counterparts. While researchers strive to adjust for factors like age, sex, health status, and education, Dr. Maggi clarifies, "We can only state that there is a strong association between the vaccine and reduced dementia, but not a causal relationship."
To address this, researchers at Stanford University utilized a "natural experiment" in Wales. In 2013, the initial shingles vaccine, Zostavax, was offered to individuals who had not yet reached the age of 80, while those aged 80 and above were ineligible. Over a seven-year period, dementia rates among those eligible for the vaccine decreased by 20%, even though only half of them actually received it. This compared to those who were excluded by mere days. "There’s no reason to think that people born a week earlier were different from those born a few days later," Dr. Maggi commented, underscoring the potential impact of the vaccine.
Further research from Australia and the United States has also identified a link between shingles vaccination and a reduced likelihood of developing dementia. In fact, the review of studies led by Dr. Maggi and her team found that several childhood and adult vaccines appear to confer similar indirect benefits. "We now know that many infections are associated with the development of dementia, whether Alzheimer’s or vascular type," she explained.
Across 21 studies involving over 104 million participants in Europe, Asia, and North America, shingles vaccination was linked to a 24% reduction in dementia risk. The influenza vaccine showed a 13% reduction, and the pneumococcal vaccine was associated with a 36% lower risk of Alzheimer’s disease. The Tdap vaccine, protecting against tetanus, diphtheria, and pertussis, was linked to a one-third decrease in dementia risk. This vaccine is recommended every 10 years for adults, and many opt for it when a grandchild is born, as newborns are not fully vaccinated in their early months.
Ongoing research is also exploring whether the shingles vaccine can reduce the risk of heart attacks and strokes, and whether the COVID-19 vaccine can improve survival rates for cancer patients.
The underlying mechanisms driving these ancillary benefits are largely hypothesized to revolve around inflammation. When the immune system is activated to combat an infection, it triggers an inflammatory response that can cause damage to surrounding tissues. Dr. Chu explains, "Damage occurs in the environment around the body’s cells, and it takes time to return to normal." The effects of this inflammation can persist long after the initial infection has cleared, potentially creating conditions conducive to other infections, or contributing to heart attacks and strokes through blood clot formation in narrowed vessels. "If you prevent the infection, you also prevent that downstream damage," she added.
Moreover, hospitalization itself—a common occurrence for older adults with infections—can lead to a loss of strength and mobility, or the development of delirium, all of which are risk factors for dementia and other health issues. Therefore, vaccines that help prevent these hospitalizations could, in turn, delay or even avert cognitive decline.
It is noteworthy that some health officials within the Trump administration have expressed skepticism towards childhood vaccines more than adult ones. However, broader public discourse and evolving policy stances on vaccination, some perceived as anti-vaccine, may have contributed to a reluctance among older adults to get vaccinated. This hesitancy means that many are not only missing out on the emerging indirect benefits but also remaining vulnerable to preventable or manageable diseases.
Dr. Schaffner, a former member of the CDC’s Advisory Committee on Immunization Practices, expressed concern, stating, "Current national vaccination policy is, at best, ambiguous, and in some aspects appears anti-vaccine." He added, "All of us who work in public health are really very concerned." The continued exploration and dissemination of information regarding these extensive benefits are crucial to ensuring that older adults can leverage the full protective potential of vaccines for a healthier and more robust aging process.