Vaccines play an increasingly vital role in protecting our health. They directly protect us against a growing number of diseases, but there is more: Evidence is accumulating that they also help keep the immune system in good condition as we age. At a certain point in life, our body’s defensive response loses effectiveness in a continuous process known as immunosenescence — the result of multiple biological processes — “among which stand out thymic involution, which reduces production of T lymphocytes capable of responding to new pathogens; an imbalance between memory immune cells and naive immune cells; accumulation of senescent cells with a proinflammatory profile; and progressive dysfunction of innate immunity, such as in macrophages or dendritic cells. Added to this are epigenetic changes, alterations in the microbiome, comorbidities, and lifestyle-related factors, which contribute to a state of low-grade chronic inflammation known as inflammaging,” Federico Martinón-Torres, MD, PhD, professor of pediatrics at the University of Santiago de Compostela and head of the pediatric department at the University Clinical Hospital of Santiago, Santiago de Compostela, Spain, and vaccine advisor to the World Health Organization, told Univadis Spain, part of the Medscape Professional Network. This process, which does not necessarily correlate with chronological age, favors the onset of severe infections and decompensation of chronic diseases, “Hence the importance of taking measures that slow or postpone aging of our immune system,” Martinón-Torres added.

This set of actions aimed at achieving healthy aging by training our immune system to respond effectively to infections or external threats, while also restoring balance after activation, is called “immunofitness.” To this end, we believe one of the keys is adding vaccines — both for their direct protection against the diseases they prevent and for their ability to train and keep our immune system finely tuned. It’s not just about avoiding illness but about preserving immune resilience. This is especially relevant in older people because aging brings progressive changes in the immune system that increase susceptibility to infection and favor complications such as hospitalizations, functional decline, or decompensation of chronic diseases, Martinón-Torres said.

For that reason, Spanish researchers led by Martinón-Torres conducted a review of the available clinical evidence on the potential role of vaccination in slowing immunosenescence. Specifically, they studied the effects of vaccination against influenza, respiratory syncytial virus (RSV), COVID, pneumococcus, herpes zoster, tetanus, diphtheria, pertussis, hepatitis B, human papillomavirus, mumps, rubella, measles, varicella, and poliomyelitis. These were chosen because they represent the main immunizations recommended for adults and older people — especially those targeting respiratory infections or agents associated with a high burden of disease, hospitalization, or death in this age group. The study’s results were recently published in the journal Human Vaccines & Immunotherapeutics.

The Role of Vaccines

First, it is essential to clarify that vaccines do not reverse biological aging of the immune system, but rather mitigate its functional consequences. They strengthen adaptive immune memory and optimize the activation of innate immunity, particularly through the use of adjuvants that stimulate a stronger response to vaccines. In addition, some vaccines can induce trained immunity phenomena that improve responses against pathogens not directly related to the vaccine antigen. “From this point of view, vaccination can be considered less an antiaging intervention and more a tool to preserve immune system function and improve resilience against the challenges associated with aging,” Martinón-Torres explained.

Vaccines Relevant to Immunofitness

All the vaccines reviewed in the study deliver multiple, undeniable benefits that far outweigh their potential side effects. However, when assessing their effects from an immunofitness perspective, “those against respiratory pathogens such as influenza, RSV, pneumococcus, and COVID, as well as the vaccine against herpes zoster, appear to have a more direct impact on preserving immune resilience in older adults by preventing events that precipitate functional decline or decompensation. Other vaccines remain essential in certain contexts, but their contribution to overall immunofitness may depend more on an individual’s risk profile. Remember, we are speaking about added benefits — that is, besides protecting against the specific disease they target, these vaccines can also provide broader health benefits,” Martinón-Torres said.

Additional Benefits in Adults

One of the most relevant aspects is the association between vaccination — especially against influenza and RSV — and reduction in cardiovascular events such as myocardial infarction or death from cardiovascular causes. There is also consistent evidence that certain vaccines, such as pneumococcal, influenza, or RSV vaccines, reduce hospitalizations for cardiorespiratory causes and can prevent exacerbations of chronic diseases. It is also striking that the herpes zoster vaccine appears to reduce the development of dementia, particularly Alzheimer’s disease — with reported reductions of about 30% in incidence, more pronounced in women — and reductions in associated mortality. “These indirect benefits of vaccines are particularly important in older people, where many severe complications are triggered by seemingly trivial infections. We are talking about diseases that, even if they do not kill, compromise autonomy and quality of life,” said Martinón-Torres.

Conclusions

Overall, the results were consistent with the hypothesis that vaccination can play a relevant role in improving immune resilience, “although we were particularly struck by the magnitude of the evidence linking influenza vaccination to reduction in cardiovascular events, as well as by emerging data that suggest broader benefits for some vaccines — such as the shingles vaccine — in areas like cognitive function. While these latter findings should be interpreted cautiously, they would nonetheless represent a very significant gain for public health,” Martinón-Torres acknowledged.

Therefore, vaccination should be considered a key preventive intervention not only against infections but also against cardiovascular events and clinical decompensation. Many exacerbations of heart failure, chronic lung disease, or diabetes are triggered by respiratory infections, so preventing these infections can indirectly reduce the burden of cardiovascular and metabolic disease. Improving immunofitness through vaccination could translate into a significant reduction in hospitalizations, complications, and healthcare resource use in an increasingly aged population.

However, we cannot place all responsibility for healthy aging on vaccination alone. A holistic approach is essential. Yes, “Vaccination should be part of routine health promotion strategies for older adults, and everyone should receive at least the vaccines available to them through free vaccination schedules. But adequate nutrition, regular physical activity, restorative sleep, avoidance of harmful habits, stress reduction, and control of chronic diseases should also be encouraged. Integrating these interventions would allow us to address functional decline associated with aging within the context of rapidly aging demographics,” Martinón-Torres concluded.

This story was translated from Univadis Spain.