By Suherman Candra Maholtra 
New clinical research presented at the American College of Cardiology’s Annual Scientific Session (ACC.26) has revealed a profound connection between the shingles vaccine and a reduced risk of catastrophic cardiovascular events. According to the study, individuals already living with heart disease who received a shingles vaccination experienced nearly half the rate of serious heart-related complications within one year compared to their unvaccinated counterparts. These findings, led by researchers at the University of California, Riverside, suggest that the benefits of the shingles vaccine extend far beyond the prevention of the painful skin condition, potentially serving as a critical tool in the secondary prevention of heart attacks and strokes.
The study analyzed an extensive dataset of more than 246,822 adults in the United States, all of whom had been diagnosed with atherosclerotic cardiovascular disease (ASCVD). This condition, characterized by the buildup of fats, cholesterol, and other substances in and on the artery walls—a process known as plaque—is the leading cause of heart attacks and strokes globally. The research adds to a burgeoning field of "immunocardiology," which explores how vaccines and the management of chronic infections can mitigate systemic inflammation and protect the vascular system.
The Biological Link Between Herpes Zoster and Vascular Health
To understand why a vaccine for shingles—a condition caused by the varicella-zoster virus (VZV)—would impact the heart, it is necessary to examine the physiological effects of the virus itself. Shingles occurs when the virus that causes chickenpox, which remains dormant in nerve tissue after the initial infection, reactivates later in life. This reactivation typically happens due to age-related declines in immunity or stress.
Medical science has long recognized that shingles infections do not merely cause a localized rash. Earlier research has demonstrated that a shingles outbreak can trigger a systemic inflammatory response. This inflammation can lead to a pro-thrombotic state, where blood is more likely to clot. Specifically, shingles infections have been shown to facilitate the formation of blood clots near the brain and heart, significantly increasing the short-term risk of myocardial infarction (heart attack), ischemic stroke, and venous thromboembolism.
By administering the shingles vaccine—either the older Zostavax or the current standard, Shingrix—patients may avoid the viral reactivation that serves as a catalyst for these dangerous clotting events. Dr. Robert Nguyen, a resident physician at the University of California, Riverside and the study’s lead author, emphasized that the protective effects are particularly pronounced in those already at high risk. "Looking at the highest risk population, those with existing cardiovascular disease, these protective effects might be even greater than among the general public," Nguyen stated.
Comprehensive Study Methodology and Population Scope
The researchers utilized TriNetX, a massive global health research network that provides access to de-identified electronic health records from millions of patients across various healthcare organizations in the United States. The study focused on a specific cohort: adults aged 50 and older who were diagnosed with atherosclerotic disease between 2018 and 2025.
The analysis was meticulously structured to ensure accuracy. Researchers identified 123,411 individuals who had received at least one dose of a shingles vaccine and matched them with an equal number of unvaccinated individuals. To ensure the groups were comparable, the team used propensity score matching, accounting for a wide range of variables including age, sex, race, and the presence of other chronic conditions such as hypertension, diabetes, and chronic kidney disease.
The primary focus of the study was the occurrence of heart-related outcomes between one month and one year following the date of vaccination (or a corresponding index date for the control group). This timeframe was selected to allow the vaccine’s immune response to stabilize while capturing the window of highest relevance for secondary prevention in cardiac patients.
A Breakdown of the Data: Quantifying the Risk Reduction
The results of the analysis showed a consistent and statistically significant reduction in cardiovascular risk across all measured metrics for the vaccinated group. The most striking finding was that vaccinated individuals were 46% less likely to experience a major adverse cardiac event (MACE)—a composite endpoint that typically includes heart attack, stroke, and cardiovascular death.
Further granular data revealed the following:
- All-Cause Mortality: Vaccinated patients showed a 66% lower risk of death from any cause during the follow-up period.
- Heart Attack (Myocardial Infarction): The risk of suffering a heart attack dropped by 32% among those who received the vaccine.
- Stroke: There was a 25% reduction in the risk of ischemic stroke.
- Heart Failure: The incidence of new or worsening heart failure was 25% lower in the vaccinated cohort.
Dr. Nguyen noted that these figures are not merely incremental; they represent a substantial shift in patient outcomes. He compared the magnitude of these benefits to the clinical improvements seen when a patient quits smoking—a cornerstone of cardiovascular health management. The data suggests that for patients already struggling with clogged arteries, the shingles vaccine could be as vital as traditional pharmaceutical interventions like statins or blood thinners.
The Evolution of Shingles Vaccination and Public Health Policy
The Centers for Disease Control and Prevention (CDC) currently recommends the recombinant zoster vaccine (Shingrix) for adults aged 50 and older. It is also recommended for adults aged 19 and older who have weakened immune systems due to disease or therapy. Shingrix, which replaced the live-attenuated Zostavax vaccine in the U.S. market around 2017-2018, is known for its high efficacy—over 90%—in preventing shingles and postherpetic neuralgia (chronic nerve pain).
The timeline of this study, spanning 2018 to 2025, largely reflects the era of Shingrix, though some patients in the database may have received the earlier Zostavax. The consistency of the findings across different years suggests that the cardiovascular benefit is a robust feature of zoster immunization.
The presentation of this data at ACC.26 comes at a time when public health officials are looking for ways to improve vaccine uptake. Despite the clear benefits, shingles vaccination rates often lag behind other immunizations like the flu shot. Dr. Nguyen suggested that these findings could provide clinicians with a powerful new talking point when discussing vaccines with hesitant patients. In an era where medical disinformation is prevalent, showing a direct link between a vaccine and the prevention of a heart attack could be the deciding factor for a patient who is primarily concerned about their cardiac health.
Addressing Limitations: The "Healthy User Bias"
While the results are compelling, the researchers acknowledged certain limitations inherent in observational studies using electronic health records. One primary concern is "healthy user bias"—the possibility that individuals who choose to get vaccinated are generally more health-conscious. These patients might be more likely to adhere to their cardiac medications, maintain a better diet, or engage in regular exercise, all of which would independently reduce their risk of heart events.
To mitigate this, the researchers adjusted for several health and socioeconomic factors, including housing stability, economic circumstances, employment status, and education levels. However, Dr. Nguyen conceded that some residual confounding might still exist. Despite this, the sheer scale of the study—involving nearly a quarter of a million people—and the dramatic 46% reduction in major events provide strong evidence that the vaccine itself is a primary driver of the improved outcomes.
Furthermore, the study’s follow-up was limited to one year. Long-term data is still being gathered, though previous studies have suggested the benefits may be durable. A 2025 study cited by the research team found that shingles vaccination was linked to a 23% reduction in cardiovascular events in generally healthy adults, with some benefits persisting for up to eight years. The current study’s focus on the high-risk ASCVD population suggests that the "bang for the buck" is significantly higher in those with pre-existing heart conditions.
Clinical Implications and Future Directions
The findings presented at ACC.26 could potentially lead to a shift in how cardiologists approach preventative care. If the shingles vaccine is confirmed to have such a high "cardioprotective" effect, it may eventually be integrated into standard post-discharge protocols for heart attack survivors or those undergoing procedures like stent placement or bypass surgery.
The concept of using vaccines to prevent heart disease is not entirely new. The influenza vaccine has already been shown in multiple studies to reduce the risk of heart attacks during flu season. However, the magnitude of the reduction seen in the shingles vaccine study is particularly high. This may be because the shingles virus remains in the body for life, unlike the seasonal flu, meaning its potential to cause chronic or episodic inflammation is much greater.
Future research will likely focus on randomized controlled trials (RCTs), which are the gold standard for medical evidence. An RCT would involve randomly assigning heart disease patients to receive either the shingles vaccine or a placebo and tracking them over several years. Such a study would eliminate the healthy user bias and provide definitive proof of the vaccine’s heart-saving capabilities.
Conclusion and Presentation Details
As the medical community gathers for the American College of Cardiology’s Annual Scientific Session, the link between infectious disease prevention and cardiovascular health remains a high-priority topic. The study titled "Herpes Zoster Vaccination and Risk of Cardiovascular Events in Patients with Atherosclerotic Cardiovascular Disease" is scheduled for a formal presentation by Dr. Nguyen on Monday, March 30.
The data serves as a reminder that the human body operates as an integrated system, where a viral infection in the nervous system can have deadly consequences for the circulatory system. For the millions of Americans living with heart disease, the simple act of receiving a shingles vaccine may offer a significant layer of protection against the world’s leading cause of death. As Dr. Nguyen concluded, "Vaccines are one of the most important medicines we have to prevent disease. These results provide another reason for patients to elect to get the vaccine."
