COVID-19 Vaccinations Linked to Decreased Heart Attack and Stroke Risk, Major UK Study Finds

In a groundbreaking study published in Nature Communications, researchers have revealed that COVID-19 vaccination is associated with a significant reduction in the incidence of heart attacks, strokes, and other cardiovascular events. This large-scale analysis, conducted by a consortium of scientists across the UK, analyzed health records of 45.7 million adults in England between December 2020 and January 2022. Contrary to persistent online misinformation, the study provides robust evidence that the benefits of COVID-19 vaccination far outweigh rare risks, especially regarding cardiovascular health.

Key Findings

Cardiovascular Event Reduction

10% Decrease in arterial thromboses (mainly heart attacks and ischemic strokes) was observed after the first vaccine dose.
Greater reductions followed second and booster doses:
- 20% risk reduction with Pfizer/BioNTech (BNT-162b2) after second doses.
- 27% risk reduction with AstraZeneca (ChAdOx1) after second doses.

Similar trends were recorded following booster doses, with hazard ratios (aHRs) indicating even lower risks of arterial and venous thrombotic events compared to pre-vaccination periods.

Venous Thrombotic Events

Incidence of pulmonary embolism and deep vein thrombosis (DVT) also dropped post-vaccination.
Reductions were more pronounced after second doses and boosters:
- Example: aHRs for venous thrombotic events were 0.68 for AstraZeneca and 0.77 for Pfizer after second doses.

Rare Side Effects Confirmed

While the study reinforced overall cardiovascular benefits, it also confirmed several rare but recognized vaccine-associated risks:

Myocarditis and Pericarditis: Elevated incidence, especially after mRNA vaccines (Pfizer and Moderna), but risks remained low and mostly transient.
Vaccine-induced thrombotic thrombocytopenia (VITT): Associated with the first dose of AstraZeneca, particularly leading to intracranial venous thrombosis.
Thrombocytopenia: Slightly higher risk noted after AstraZeneca’s first dose but not after subsequent doses.

Importantly, these rare side effects were far less frequent compared to the cardiovascular risks posed by COVID-19 infection itself.

Methodology

Researchers utilized comprehensive longitudinal health records covering primary care visits, hospital admissions, COVID-19 tests, prescriptions, and death registrations.
Statistical adjustments were made for age, sex, ethnicity, co-morbidities, previous COVID-19 infection, and medication use.
Data were sourced from NHS England’s Secure Data Environment, ensuring patient privacy and robust record linkage.
Analyses used Cox regression models to estimate adjusted hazard ratios over specific post-vaccination intervals (1-4 weeks, 5-12 weeks, 13-24 weeks).

The study design aimed to minimize confounding biases and featured sensitivity analyses to address potential influences like public announcements about vaccine safety.

Context and Implications

This cohort study adds to a growing body of evidence that COVID-19 vaccines save lives not just by preventing infection, but also by protecting against serious cardiovascular events. It counters earlier fears stoked by isolated reports of vaccine side effects.

According to study co-author Dr. Samantha Ip, the findings offer “further support for the effectiveness and safety of the COVID-19 vaccination programme” and affirm the public health value of mass vaccination campaigns.

Notably:

COVID-19 infection itself is strongly linked to an increased risk of heart attacks, strokes, and blood clots.
Vaccination likely mitigates these risks by preventing severe infections, thus lowering systemic inflammation and clotting disturbances associated with COVID-19.

Strengths and Limitations

Strengths:

Massive sample size (45.7 million individuals) allowed for reliable analysis of both common and rare events.
Detailed health record linkage across multiple care settings.
Adjustment for a wide range of confounding factors.
Publicly available pre-specified protocol and code, enhancing transparency.

Limitations:

Some residual confounding may persist despite adjustments.
Outcome misclassification is possible due to limitations in routine electronic health records.
Underreporting of mild or non-hospitalized events could have occurred.
The study does not address long-term safety beyond 26 weeks post-vaccination.

Source: Nature