Study Says COVID-19 Vaccines Can Reduce Risk of Heart Failure, Blood Clots Following Infection


COVID-19 vaccination was associated with reduced risks of acute and post–acute COVID-19 heart failure, venous thromboembolism, and arterial thrombosis/thromboembolism.

A recent study revealed that COVID-19 vaccines reduce the likelihood of heart failure (HF) by as much as 55% and blood clot formation by up to 78% after COVID-19 infection.

COVID-19 vaccine | Image credit: Leigh Prather –

COVID-19 vaccine | Image credit: Leigh Prather –

Published in BMJ Heart, the study found that COVID-19 vaccination was associated with reduced risks of acute (30-day) HF by 55%, venous thromboembolism (VTE) by 78%, and arterial thrombosis/thromboembolism (ATE) by 47%. These reduced risks are in comparison with patients who were not vaccinated against COVID-19.

“In line with previous studies, our findings suggest a potential benefit of vaccination in reducing the risk of post–COVID-19 thromboembolic and cardiac complications,” the researchers said.

The staggered cohort study included a total of 10.17 million vaccinated and 10.39 million unvaccinated individuals from the United Kingdom, Spain, and Estonia. Subdistribution hazard ratios (sHRs) were estimated using Fine-Gray models, and random-effect meta-analyses were conducted across staggered cohorts and databases.

Looking forward to the postacute phases—31 to 90 days, 91 to 180 days, and 181 to 365 days post COVID-19 infection—HF and VTE both saw slight dips in reduced risks at 180 days, which went back up slightly at the 365-day mark. Reduced risks remained notable.

For HF, a 39% reduced risk persisted at 90 days and 180 days, which then went back up to a 48% reduced risk at 1 year after COVID-19 infection. For VTE in the postacute phase, patients had a 57% reduced risk at 90 days, dropping to 47% at 180 days, with a slight uptick to a 50% reduced risk at 1 year.

The researchers saw a slightly different trend with ATE. After dropping from a 47% 30-day risk to a 26% 90-day risk, the postacute reduced risk associated with COVID-19 vaccination increased to 28% at 180 days, increasing to a 38% reduced risk at 1 year post infection.

The researchers included post–COVID-19 outcome events based on previous research. Among these were myocarditis/pericarditis (MP), ventricular arrhythmia/cardiac arrest (VACA), deep vein thrombosis (DVT), pulmonary embolism (PE), ischemic stroke (IS), and myocardial infarction (MI). All of these saw reduced risks in the 30-day acute phase for vaccinated individuals.

Compared with unvaccinated individuals, meta-analytic estimates in the acute phase showed sHRs of:

  • 0.41 (0.26-0.66) for MP
  • 0.41 (0.27-0.63) for VACA
  • 0.36 (0.28-0.45) for DVT
  • 0.19 (0.15-0.25) for PE
  • 0.55 (0.43-0.70) for IS
  • 0.49 (0.38-0.62) for MI

The study has limitations inherent to real-world data, such as data quality issues and potential confounding factors. Despite using advanced methods like large-scale propensity score weighting and calibration, the researchers said there may have still been residual bias. Under-reporting of post–COVID-19 complications—particularly in primary care databases without hospital linkage—could also affect the accuracy of outcomes, but results from databases including secondary care data showed similar trends. Additionally, the study included a small number of young men and male teenagers, a population of interest due to concerns about increased risks of myocarditis/pericarditis following vaccination.

“Vaccination against SARS-CoV-2 substantially reduced the risk of acute post-COVID-19 thromboembolic and cardiac complications, probably through a reduction in the risk of SARS-CoV-2 infection and the severity of COVID-19 disease due to vaccine-induced immunity,” the researchers concluded. “Findings from this study highlight yet another benefit of COVID-19 vaccination. However, further research is needed on the possible waning of the risk reduction over time and on the impact of booster vaccination.”


Mercadé-Besora N, Li X, Kolde R, et al. The role of COVID-19 vaccines in preventing post-COVID-19 thromboembolic and cardiovascular complications. Heart. Published online March 12, 2024. doi:10.1136/heartjnl-2023-323483

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