Updated Covid Vaccines Significantly Reduce Risk of Heart Attacks and Strokes, Large Study Finds

A landmark analysis of more than one million U.S. veterans has delivered compelling evidence that updated Covid-19 vaccines offer substantial protection against severe cardiovascular disease. Published in JAMA Internal Medicine, the study found that patients who received the 2024-2025 Covid-19 vaccine formulation had a 38% lower risk of experiencing a Covid-associated major adverse cardiovascular event (MACE) compared to those who only received a flu shot.[1][2][3]

The MACE composite endpoint tracked by researchers included cardiovascular death, heart attacks, strokes, and hospitalizations for heart failure. The protective effect was most pronounced among older adults; for patients over the age of 75, the vaccine's effectiveness against these severe cardiac outcomes reached nearly 51%, translating to a significant absolute risk reduction in a highly vulnerable population.[2][3]

However, the study's most surprising finding extended beyond cases with a confirmed Covid-19 diagnosis. Researchers discovered that vaccinated veterans experienced a nearly 24% reduction in all-cause cardiac events. This means the vaccinated cohort had significantly fewer heart attacks and strokes overall, regardless of whether a Covid-19 infection was ever documented in their medical records.[1][3]

Dr. Ziyad Al-Aly, the study's lead investigator and a clinical researcher at the VA St. Louis Health Care System, proposed a mechanism for this broad protective effect. He argues that a significant fraction of cardiac events currently classified by hospitals as "idiopathic"—meaning they have no known origin—are actually downstream consequences of unrecognized SARS-CoV-2 infections.[1][6]

Because the SARS-CoV-2 virus binds to ACE2 receptors found on endothelial cells and heart muscle, even mild or asymptomatic infections can trigger systemic inflammation and disrupt blood clotting. This vascular injury can precipitate a heart attack or stroke weeks later. By blunting the initial infection and reducing viral replication, the vaccine prevents this dangerous inflammatory cascade from taking hold.[1][5]

These findings align with a growing body of international evidence regarding the cardiovascular safety and benefits of Covid-19 immunization. A previous comprehensive study published in Nature Communications, which analyzed the health records of 46 million adults in England, similarly concluded that the incidence of arterial thromboses—such as heart attacks and strokes—was substantially lower in the months following vaccination.[4][6]

The JAMA study also provides critical context regarding vaccine safety, specifically addressing early concerns about myocarditis, an inflammation of the heart muscle. While a rare myocarditis signal was observed in young males following the original mRNA vaccine doses in 2021, extensive monitoring shows that this risk has largely resolved with the updated formulations.[1][4]

Current data indicates that the myocarditis rate associated with the 2024-2025 and 2025-2026 vaccine versions is at or below two cases per million doses. This figure is indistinguishable from the background rate of myocarditis in the general population. In stark contrast, a Covid-19 infection itself causes myocarditis at a rate roughly 20 times higher than the vaccine, and infection-induced cases are consistently more severe.[1][5][6]

Despite these documented cardiovascular benefits, public health officials face a significant challenge in communicating this risk-benefit profile to the public. Uptake of the updated Covid-19 vaccines remains well below that of the annual flu shot, even among older demographics who stand to gain the most absolute risk reduction.[1][2]

For practicing clinicians, the evidence pack is becoming increasingly clear: the Covid-19 vaccine is no longer just a shield against acute respiratory distress. It is emerging as a vital component of secondary cardiovascular prevention, offering a proven method to reduce the compounding burden of heart disease in an era where the virus continues to circulate.[2][5][6]