Heart Attacks And Strokes Declined After COVID-19 Vaccinations, Scientists Find

When the COVID-19 vaccine rollout began, the primary goal was clear: to prevent infection, reduce hospitalizations, and save lives. Over time, attention also turned to vaccine safety, particularly concerning potential cardiovascular side effects. Headlines focused on rare cases of myocarditis and clotting disorders, sparking understandable concern. But now, one of the most comprehensive studies to date—drawing on health records from over 45 million adults in England—offers a fuller, more nuanced picture.

The study not only confirms that these rare adverse events remain limited and well-characterized, but also reveals something more profound: COVID-19 vaccination was associated with a reduction in the incidence of major cardiovascular events, including heart attacks, strokes, and dangerous blood clots. These benefits were consistent across different age groups, vaccine brands, and doses, and appeared to strengthen with second and booster vaccinations.

This emerging evidence challenges earlier assumptions and reframes the conversation. Rather than posing a net cardiovascular risk, COVID-19 vaccination may, in fact, protect against some of the most serious health threats people face today. In the sections that follow, we explore how these findings were uncovered, what they mean for individual and public health, and why they matter as we shape the future of vaccination policy and communication.

A Clear Trend Toward Protection

Large-scale evidence from England’s national health records reveals a striking pattern: COVID-19 vaccination was associated with a reduced risk of major cardiovascular events, including heart attacks and strokes. Based on anonymized data from over 45 million adults between December 2020 and January 2022, researchers found that the incidence of both arterial and venous thrombotic events declined following each vaccine dose—first, second, and booster. These findings, drawn from one of the world’s most comprehensive population datasets, offer strong reassurance about the broader health benefits of vaccination beyond its role in infection control.

These protective effects were consistent across different vaccine brands—ChAdOx1, BNT-162b2, and mRNA-1273—and became more pronounced with additional doses. For instance, 13–24 weeks after the second dose, the adjusted risk of arterial thrombotic events dropped by approximately 27% with ChAdOx1 and 20% with BNT-162b2, compared to periods before vaccination. Venous events, such as pulmonary embolism and deep vein thrombosis, showed a similarly reduced incidence. These results held even after adjusting for numerous confounding factors, including age, comorbidities, and prior COVID-19 infection.

While the mechanisms driving this decline will be explored further in the next sections, a major factor appears to be the vaccine’s ability to prevent COVID-19 itself. The virus is known to trigger vascular inflammation and clotting abnormalities, significantly increasing cardiovascular risks. By preventing or lessening the severity of infection, vaccination indirectly offers a measurable cardioprotective effect—a benefit that may not have been fully appreciated during early vaccine rollout discussions.

Dissecting the Details – Which Cardiovascular Events Declined, and When

A closer look at the data reveals that the decline in cardiovascular events after COVID-19 vaccination wasn’t uniform—it varied by event type, timing after vaccination, and vaccine brand. The most notable reductions occurred in arterial thrombotic events, such as acute myocardial infarction (AMI) and ischemic stroke, which are among the leading causes of death and disability globally. These events saw a clearer decline after the second and booster doses, suggesting that continued immunization amplified the protective effect.

For example, the risk of arterial events dropped most significantly in the weeks following the second and booster doses of both ChAdOx1 and BNT-162b2 vaccines. In people who received two doses of ChAdOx1, the adjusted hazard ratio (aHR) for arterial thrombosis was 0.73 at 13–24 weeks post-vaccination—indicating a 27% lower risk compared to the unvaccinated or pre-vaccination period. Similar reductions were observed with BNT-162b2. Venous thrombotic events, including pulmonary embolism and deep vein thrombosis, followed a parallel trend. The booster doses were especially effective: people who received a primary course of ChAdOx1 followed by an mRNA booster had aHRs as low as 0.55 to 0.63 for venous events in the weeks following their booster.

Importantly, these benefits were consistent across different demographics, including age groups and people with prior medical conditions. The data showed little variation in cardiovascular risk reduction across ethnic backgrounds, with a few exceptions noted in smaller subgroups. Men generally had slightly higher baseline risks than women, but the protective effect of vaccination was evident across both sexes. This consistency strengthens the credibility of the findings and suggests that the cardioprotective effects of COVID-19 vaccines are broadly applicable across the population.

A Closer Look at Rare Risks – Myocarditis, Pericarditis, and Thrombosis

While the overall cardiovascular impact of COVID-19 vaccination was protective, the study also confirmed the presence of rare but real vaccine-associated risks, consistent with previous regulatory findings. These included myocarditis and pericarditis following mRNA vaccines (like BNT-162b2 and mRNA-1273), and vaccine-induced thrombotic thrombocytopenia (VITT) following the adenovirus-based ChAdOx1 vaccine.

The most notable increase in myocarditis risk occurred within one week after the second dose of the BNT-162b2 vaccine, where the adjusted hazard ratio (aHR) peaked at 3.14—more than triple the baseline risk. A similar, though less pronounced, spike was seen after mRNA booster doses. Pericarditis also rose slightly in the immediate weeks following both first and second doses of BNT-162b2 and ChAdOx1, particularly in younger adults. However, these increases were generally short-lived and the absolute number of cases remained very low, especially when compared to the number of doses administered.

VITT, a rare and serious clotting condition characterized by thrombosis and low platelet counts, was observed almost exclusively after the first dose of ChAdOx1. The highest incidence occurred within two weeks post-vaccination, with an aHR of 5.92 for intracranial venous thrombosis (ICVT). Importantly, this risk was not seen with the second dose of ChAdOx1 or with any mRNA vaccine, underscoring the dose-specific and brand-specific nature of these rare complications.

Crucially, the researchers found no evidence of new cardiovascular risks emerging after second or booster doses, and no unknown adverse outcomes beyond what had already been documented by global regulators. For clinicians and the public alike, these findings reaffirm that while rare events exist and must be monitored, they are far outweighed by the benefits of vaccination—particularly in preventing the far more common and severe cardiovascular complications linked to COVID-19 infection itself.

The Hidden Cardiovascular Threat of COVID-19 – And How Vaccines Offset It

One of the most important, and often underappreciated, reasons behind the cardiovascular benefit of COVID-19 vaccines is their role in preventing the infection itself. Multiple studies have established that COVID-19 is not merely a respiratory illness—it can trigger widespread inflammation and blood clotting, significantly raising the risk of heart attacks, strokes, and other vascular complications, sometimes weeks or months after recovery.

This heightened cardiovascular risk following COVID-19 infection has been observed across different age groups and health profiles. In fact, research published in journals such as Nature Medicine and The Lancet has shown that individuals recovering from even mild cases of COVID-19 may experience increased risk of cardiovascular events for up to a year after infection. These risks are particularly elevated among those who had severe or hospitalized COVID-19, but they are not limited to that group.

By preventing infection in the first place—or at least reducing its severity—vaccines interrupt this dangerous chain of events. In doing so, they help shield the heart and vascular system from the longer-term damage COVID-19 can cause. This indirect benefit, while harder to quantify precisely in individual cases, plays a substantial role in the overall reduction in cardiovascular events observed in vaccinated populations. In short, vaccines may be doing more than just keeping people out of the ICU—they may be keeping their arteries and hearts healthier as well.

What This Means for Vaccine Policy and Public Trust

As COVID-19 transitions from pandemic to endemic, healthcare systems worldwide are recalibrating their vaccination strategies. The findings from this large-scale study underscore a compelling point: maintaining broad vaccine coverage, particularly among older adults and individuals with underlying health conditions, may yield benefits beyond infection prevention. By reducing the incidence of serious cardiovascular events such as heart attacks, strokes, and venous thromboembolism, vaccination could play a critical role in lowering the overall burden of disease on both individuals and healthcare systems. This expanded understanding reinforces the public health value of booster campaigns, especially during periods of viral resurgence.

The study also carries important implications for vaccine communication and public trust. In recent years, vaccine hesitancy has been fueled by misinformation, fragmented data, and legitimate—but sometimes overstated—concerns about side effects. Transparent, population-wide studies like this one are essential to restoring confidence. By quantifying both benefits and rare risks with precision and nuance, this research gives health professionals and policymakers credible data to share with the public. Crucially, it confirms that the rare complications—such as myocarditis and vaccine-induced thrombosis—are not only uncommon but have remained stable and well-documented since early in the vaccine rollout.

Looking ahead, these findings invite us to rethink how we define the value of vaccination. While the primary goal of COVID-19 vaccines has been to reduce hospitalizations and deaths from infection, the additional benefit of lowering non-infectious complications—particularly cardiovascular events—suggests a broader potential for vaccines as tools in preventive medicine. This opens new avenues for how we measure vaccine effectiveness and health policy priorities, especially as global populations age and chronic disease burdens grow. In this light, continued investment in vaccine access, uptake, and education becomes not just a pandemic response, but a long-term strategy for healthier societies.