On June 15, 2026, a team led by Ziyad Al-Aly at the VA St. Louis Health Care System and Washington University published a study in JAMA Internal Medicine that should, by any reasonable standard, settle a debate that has surrounded COVID-19 vaccination since its introduction.
The study followed 1,039,659 US veterans, 349,085 who received the 2024-2025 updated COVID-19 vaccine alongside their influenza vaccine, and 690,574 who received only the influenza vaccine. Over eight months of follow-up, the vaccinated group experienced a 37.7% reduction in COVID-19-associated major adverse cardiovascular events (MACE), a composite of cardiovascular death, myocardial infarction, stroke, and hospitalisation for heart failure. The relative risk reduction for cardiovascular death alone was 57.9%.
At the population level, the researchers estimate that vaccination could prevent approximately 2,370 MACE events and 1,580 deaths per million people over eight months, or roughly 3,500 cardiac events and 2,400 deaths per million per year.
The study is not small. It is not short. It is not a subgroup analysis or a meta-analysis of heterogeneous trials. It is a large, well-designed retrospective cohort study using target-trial emulation and inverse probability weighting, methods that, while not a substitute for randomisation, are designed to minimise the healthy-vaccinee bias that plagues observational vaccine research. The authors conducted 12 sensitivity analyses, including overlap weighting, doubly robust estimation, and negative control analyses (showing no association between vaccination and influenza-related outcomes, as expected), all of which supported the main finding.
Safety Has Been Demonstrated
The finding that COVID-19 vaccination protects the heart is not new. It is the latest and largest entry in a body of evidence that now stretches back years and spans hundreds of millions of doses administered globally. Study after study, from the CDC, from European health agencies, from independent academic groups, has shown that the rare cardiac adverse events associated with mRNA vaccines (myocarditis and pericarditis, predominantly in young males, typically mild and self-limiting) are far outweighed by the cardioprotective effects of preventing severe COVID-19.
What is notable about the Al-Aly study is its timing: it evaluated the 2024-2025 updated vaccines against the variants circulating in late 2024, at a point when population immunity from prior infection and vaccination was already high. Despite this baseline protection, the updated vaccine still provided a measurable cardiovascular benefit, particularly in adults over 75, where the risk reduction for COVID-associated MACE reached 50.7%.
Dr Robert Califf, former FDA Commissioner, wrote an accompanying commentary stating that the study offers “convincing evidence that the cardiovascular benefits of vaccination for COVID-19 are much greater than the risks, demonstrated or potential, that have been identified.”
The Absolute Numbers
It is important to be precise about what the study found. The relative risk reduction of 37.7% for COVID-associated MACE corresponds to an absolute risk reduction of 2.0 events per 10,000 people, a small number in absolute terms, because the baseline risk of COVID-associated cardiac events was already low in a predominantly vaccinated, partially immune population. For all-cause MACE (any cardiac event, regardless of COVID documentation), the absolute reduction was larger: 23.7 fewer events per 10,000 people, reflecting protection against unrecognized SARS-CoV-2 infections driving cardiac complications.
These are not numbers that make dramatic headlines. A 2-in-10,000 absolute risk reduction does not sound like much, until you multiply it across a population of 300 million and consider that the alternative intervention, not vaccinating, carries no comparable protective effect. At scale, 2-in-10,000 becomes thousands of heart attacks and strokes prevented.
The Persistence of Fear
And yet, five years after the first COVID-19 vaccines were authorised, a substantial portion of the public remains convinced that the vaccines are dangerous to the heart. The narrative that mRNA vaccines cause cardiac damage, driven by the very real but rare occurrence of vaccine-associated myocarditis, amplified by social media algorithms and political polarisation, has proven extraordinarily resistant to data.
The JAMA study addresses this head-on. By demonstrating that vaccinated individuals had fewer cardiac events than unvaccinated individuals, not just similar rates, but fewer, it provides the strongest possible counterargument to the claim that the vaccines impose a net cardiac risk. The study did not specifically evaluate rare safety outcomes like myocarditis, which the authors note is beyond its scope and the subject of ongoing analyses. But it evaluated the thing that matters most for population health: whether vaccination, on net, protects the cardiovascular system. The answer is yes.
The persistence of the fear narrative despite accumulating evidence raises a question that goes beyond epidemiology. At what point does the burden shift from the scientific community to provide more evidence, to the authorities responsible for communicating risk to the public? When a body of evidence encompasses more than a million patients, multiple study designs, years of follow-up, and consistent findings across independent research groups, continuing to treat the safety question as open is no longer scientific caution. It is a failure of communication that has public health consequences.
Sources:
1. Cai, M., Xie, Y. & Al-Aly, Z. “2024-2025 COVID-19 Vaccine and Major Adverse Cardiovascular Events Among US Veterans.” JAMA Internal Medicine, June 15, 2026. DOI: 10.1001/jamainternmed.2026.1929
2. Califf, R. Editorial commentary. JAMA Internal Medicine, June 15, 2026.
3. Cai, M., Xie, Y. & Al-Aly, Z. “Effectiveness of 2024-2025 COVID-19 Vaccination Against Severe COVID-19.” New England Journal of Medicine, October 8, 2025. DOI: 10.1056/NEJMoa2510226
4. Chan, L. “Covid Vaccination Cut Risk of Adverse Heart Events, Large Study Finds.” STAT News, June 15, 2026. https://www.statnews.com/2026/06/15/covid-vaccination-cardiovascular-protection-jama-study/