Risk of heart attack, stroke drops after COVID vaccination, data show

A study today involving 46 million adults in England shows that the incidence of both heart attacks and strokes dropped following COVID-19 vaccination compared to the incidence before or without vaccination.

The study authors said the incidence of common cardiovascular diseases dropped after every COVID-19 vaccination, but COVID-19 vaccination was associated with slightly increased rates of myocarditis and pericarditis following mRNA-based vaccines, and vaccine-induced thrombotic thrombocytopenia following adenovirus-based vaccines such as the AstraZeneca vaccine.

The study was based on findings from the British Heart Foundation (BHF) Data Science Centre at Health Data Research UK, with researchers analyzing de-identified health records from 45.7 million adults in England from December 8, 2020, to January 23, 2022. 

During that period, 90% of UK adults were vaccinated with at least one dose of COVID-19 vaccines from Pfizer, Moderna, or AstraZeneca.

Among the study participants, 37.3 million people received a first vaccination and were eligible for the second dose during the study period.

Risk lowest in first weeks after vaccination 

Patients had 5,655 arterial and 21,230 venous thrombotic events during the study period. Other less frequent cardiac events included 1,885 cases of thrombocytopenia, 590 of myocarditis, and 455 of pericarditis.

Adjusted hazard ratios (aHRs) for arterial thrombotic events 13 to 24 weeks after first vaccine dose were 0.99 (95% confidence interval [CI], 0.97 to 1.02) after AstraZeneca, and 0.90 (0.88 to 0.93) after Pfizer vaccines. Corresponding aHRs after second doses were 0.73 (0.70 to 0.76) and 0.80 (0.77 to 0.83), respectively, the authors said. 

“For all vaccine brands and doses, aHRs in the first few weeks were lower than in later weeks,” the authors said.

As seen in other studies, there was a higher incidence of thrombocytopenia after first dose of AstraZeneca compared with no vaccination, with greatest aHR 2 weeks after vaccination (2.07; 95%, CI 1.67 to 2.58). Similarly, the incidence of myocarditis was higher after first dose of the Pfizer vaccine, with greatest aHR 1 week after vaccination (2.05; 95% CI, 1.28 to 3.29).

Those findings, however, should not affect wide recommendations for COVID-19 vaccination, the authors said. 

“This England-wide study offers patients reassurance of the cardiovascular safety of first, second and booster doses of COVID-19 vaccines,” coauthor William Whiteley, MB BCh, PhD, of the University of Edinburgh, said in a press release from Health Data Research UK. “It demonstrates that the benefits of second and booster doses, with fewer common cardiovascular events include heart attacks and strokes after vaccination, outweigh the very rare cardiovascular complications.”

“This England-wide study offers patients reassurance of the cardiovascular safety of first, second and booster doses of COVID-19 vaccines.

Co-senior author Venexia Walker, PhD, MMath, with the University of Bristol, added, “Given the critical role of COVID-19 vaccines in protecting people from COVID-19, it is important we continue to study the benefits and risks associated with them.”