"Vaccines are powerful tools not just for preventing specific infections, but for promoting overall healthy aging by reducing inflammation and its cascading negative effects on the body and brain."
Recent research is illuminating a fascinating aspect of vaccinations: their "indirect benefits." Beyond the primary goal of protecting against a particular disease, vaccines are increasingly showing positive ripple effects that enhance overall health, particularly for older adults. These findings suggest that vaccinations are not merely shields against illness, but rather proactive investments in long-term well-being, potentially mitigating risks for serious chronic conditions and cognitive decline.
Vaccines Offer More Than Direct Protection: Unveiling the Indirect Health Advantages
While the primary purpose of vaccines is to confer direct protection against specific pathogens, a growing body of scientific evidence suggests they offer a surprising array of secondary health benefits, particularly for older adults. These "indirect benefits" extend beyond preventing the immediate illness for which a vaccine is designed, impacting overall health, cognitive function, and even cardiovascular well-being. As research in this area accelerates, it is becoming clear that vaccines are potent tools for promoting healthy aging and potentially delaying or preventing significant age-related health challenges.
The most direct and compelling reason for adults to get vaccinated remains the robust protection they offer against specific diseases. For instance, two doses of the shingles vaccine provide approximately 90% efficacy against this painful, blistering infection, which can lead to debilitating long-term nerve pain and other serious complications. Given that shingles will affect one in three Americans in their lifetime, this level of protection is substantial. Similarly, the respiratory syncytial virus (RSV) vaccine significantly reduces the risk of hospitalization for older adults, with efficacy rates near 70% in the first year post-vaccination and around 60% in the subsequent two years. The annual flu vaccine, while variable in effectiveness depending on the precise match to circulating strains, reliably reduces the severity of illness, a crucial benefit for a population more vulnerable to influenza complications.
However, the landscape of vaccine benefits is expanding to include these less obvious, yet profoundly important, indirect effects. These emerging advantages are the subject of intense scientific scrutiny, with studies accumulating rapidly over the past decade. Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center, notes the acceleration of research in this domain. While some of these protective effects are supported by decades of data, others are emerging from more recent studies, with their full implications still under investigation. The RSV vaccine, for example, only became available in 2023, marking it as a prime candidate for ongoing research into its broader health impacts.
Dr. Stefania Maggi, a geriatrician and senior researcher at the National Research Council’s Neuroscience Institute in Padua, Italy, emphasizes the consistency of these findings. She is the lead author of a significant meta-analysis published in the journal Age and Ageing, which identified a reduced risk of dementia following vaccination against various diseases. Maggi posits that these "downstream effects" position vaccines as critical instruments for fostering healthy aging and preventing both physical and cognitive deterioration.
Despite the growing evidence, a concerning number of older adults remain under-vaccinated. This is particularly troubling given that their immune systems are naturally weaker, and the prevalence of chronic conditions often heightens their susceptibility to infectious diseases. Data from the Centers for Disease Control and Prevention (CDC) in mid-December revealed that approximately 37% of older adults had not yet received their annual flu vaccine. Vaccination rates for RSV were even lower, with only 42% having received it at some point, and fewer than a third had received the most recent COVID-19 vaccine. Similarly, despite CDC recommendations for a single dose of the pneumococcal vaccine for adults aged 50 and over, a study in the American Journal of Preventive Medicine estimated that only 12% of individuals aged 67-74 and a mere 8% of those over 75 had received it between 2022 and 2024, following updated recommendations.
One of the most robust areas of evidence for indirect benefits comes from the influenza vaccine, with data spanning 25 years demonstrating a reduction in cardiovascular risk. Healthy older adults who receive the flu shot exhibit a significantly lower risk of hospitalization for heart failure, as well as pneumonia and other respiratory infections. Studies have also linked flu vaccination to a reduced risk of heart attack and stroke. It is important to note that much of this research predates the availability of the more potent influenza vaccines currently recommended for older adults, suggesting that the benefits may be even greater with contemporary formulations.
The question then arises: could the RSV vaccine, also targeting a respiratory illness, offer similar cardiovascular advantages? A large-scale study conducted in Denmark on older adults found a nearly 10% reduction in cardiorespiratory hospitalizations (affecting both the heart and lungs) among vaccinated individuals compared to a control group – a statistically significant decrease. However, the reduction in cardiovascular disease and stroke hospitalizations did not reach statistical significance. Dr. Helen Chu, an infectious disease specialist at the University of Washington and co-author of a related editorial in JAMA, suggests this might be due to a short follow-up period or inadequate diagnostic testing. Chu believes that RSV is unlikely to behave fundamentally differently from influenza in its systemic effects and anticipates that further data on RSV vaccination will likely reveal similar, if not greater, protective effects.
Vaccination against COVID-19, another dangerous respiratory illness, has also been associated with a reduced risk of developing "long COVID," a debilitating condition that can affect both physical and mental health.
Perhaps the most provocative findings relate to the shingles vaccine. Last year, researchers highlighted an association between this vaccine and lower rates of dementia, even with an older, less effective version of the vaccine that has since been replaced by Shingrix. The majority of studies exploring indirect benefits are observational. This is due to ethical constraints, as researchers cannot deny a safe and effective vaccine to a control group that could potentially develop the targeted disease. Consequently, results may be influenced by the "healthy volunteer bias," where vaccinated individuals may exhibit other healthy behaviors that differentiate them from their unvaccinated counterparts. While researchers attempt to adjust for factors like age, sex, health status, and education, as Dr. Maggi explains, "we can only state that there is a strong association between the vaccine and a reduction in dementia, but not a causal relationship."
However, a natural experiment in Wales provided compelling evidence. In 2013, the first shingles vaccine, Zostavax, was offered to individuals under 80 years old, with those aged 80 and over being ineligible. Over a seven-year period, dementia rates decreased by 20% among those eligible for the vaccine, even though only half actually received it, compared to those who narrowly missed eligibility. Maggi points out, "There is no reason to believe that individuals born a week earlier were different from those born a few days later." Further studies in Australia and the United States have also observed that shingles vaccination reduces the likelihood of developing dementia.
In Maggi’s comprehensive review of studies, several childhood and adult vaccines appear to confer similar benefits. "We now know that many infections are associated with the development of dementia, whether it’s Alzheimer’s or vascular dementia," 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, while the pneumococcal vaccine was associated with a 36% lower risk of Alzheimer’s disease. The Tdap vaccine (tetanus, diphtheria, and acellular pertussis) demonstrated a one-third decrease in dementia risk. Adults are recommended to receive a Tdap booster every 10 years, often administered when a grandchild is born, as newborns are not fully vaccinated in their early months.
Ongoing research is exploring whether the shingles vaccine also reduces the risk of heart attack and stroke, and whether COVID-19 vaccination improves survival rates for cancer patients.
The underlying mechanisms for these additional vaccine benefits are largely hypothesized to revolve around inflammation. When the immune system activates to fight an infection, it triggers an inflammatory response that can damage surrounding tissues. Dr. Chu explains, "There is damage to the environment around the body’s cells, and it takes time to return to normal." The effects of inflammation can persist long after the initial infection, potentially facilitating the development of 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 subsequent damage," Chu adds.
Hospitalization itself can be a risk factor for dementia and other health issues in older adults, leading to loss of strength, mobility, and the onset of delirium. Therefore, vaccines that help prevent hospitalization could potentially delay or even prevent cognitive decline.
Concerns have been raised about the impact of public health messaging on vaccination rates. Some health officials have expressed skepticism towards childhood vaccines, a stance that may have inadvertently contributed to hesitancy among older adults. This hesitancy means many are not only missing out on the emerging indirect benefits of vaccination but also remain vulnerable to the very diseases that vaccines are designed to prevent or mitigate. Dr. Schaffner, a former member of the CDC’s Advisory Committee on Immunization Practices, expressed deep concern, stating, "The current national policy on vaccination is, at best, ambiguous, and in some aspects appears anti-vaccine." This sentiment is shared by public health professionals who are worried about the implications for population health.
The New Old Age is produced in collaboration with The New York Times.