Cardiovascular Effects of COVID-19 Vaccines: A Study of 46 Million People

COVID-19 vaccines remain a subject of debate. Yet during the most difficult phases of the pandemic, when hospitals and intensive care units were overwhelmed, vaccines came to our aid. Despite this scientific achievement, which saved millions of lives within a short time, vaccines are now the target of a widespread smear campaign. Scientific evidence, however, shows that vaccines not only prevent COVID-19 but also reduce many cardiovascular risks .

According to a large cohort study published in July 2024 in Nature Communications, initial doses of COVID-19 vaccines generally reduced cardiovascular events, although certain complications could occur in rare cases.

A Study Covering 46 Million People

Although COVID-19 vaccines have saved millions of lives, they are known to be associated with certain rare side effects. This study examined the health records of nearly 46 million adults in England to assess the cardiovascular safety of different vaccine doses and brand combinations. It specifically investigated associations between first doses, second doses and boosters and thrombotic and cardiovascular complications.

Main Findings

• Fewer thrombotic events: The incidence of arterial thrombotic events, such as acute myocardial infarction (heart attack) and ischemic stroke, decreased after each vaccine dose.
  • Arterial thrombotic events after the second dose :
    • Pfizer-BioNTech (BNT-162b2): 20% reduction (aHR: 0.80; 95% CI: 0.77–0.83)
    • Moderna (mRNA-1273): 27% reduction (aHR: 0.73; 95% CI: 0.70–0.76)
• Fewer venous thrombotic events: The incidence of venous thrombotic events, including pulmonary embolism and deep vein thrombosis (DVT), also fell after vaccination.
  • Venous thrombotic events (pulmonary embolism, DVT):
    • After the Pfizer-BioNTech (BNT-162b2) booster: 44% reduction (aHR: 0.56; 95% CI: 0.49–0.63)
    • After the Moderna (mRNA-1273) booster: 42% reduction (aHR: 0.58; 95% CI: 0.45–0.74)
• Rare complications:
  • The first dose of the adenovirus-based ChAdOx1 (AstraZeneca) vaccine was associated with rare vaccine-induced thrombotic thrombocytopenia (VITT). This vaccine was not used in Türkiye.
  • mRNA vaccines (BNT-162b2 [Pfizer-BioNTech] and mRNA-1273 [Moderna]) were rarely associated with myocarditis and pericarditis, inflammation of the heart muscle and its surrounding sac, particularly after the first and second doses.
  • These effects were more frequent in young men.

Clinical and Public Health Implications

• Because the cardiovascular risks of COVID-19 infection itself are much greater than the possible rare side effects of vaccines, vaccination programs should be supported for broad populations.
• Better monitoring mechanisms could be established, particularly for higher-risk people, including those with chronic illnesses and older adults.
• Rare vaccine-associated complications should be monitored regularly, while the importance of vaccination should be emphasized because of its overall cardiovascular protective effect.

This study strongly supports the overall cardiovascular safety of vaccines and their effectiveness in reducing COVID-19-related cardiovascular risks.