The risks of getting a blood clot if you contradict COVID-19 is far greater than if you receive the Pfizer-BioNTech and AstraZeneca vaccines, according to a new BMJ study.
The peer-reviewed study analyzed 30 million people vaccinated in England between December 2020 and April 2021. Researchers accounted for the hospitalization rates or death from blood clots, as well as other blood disorders, within 28 days of either a positive COVID-19 test or receiving the first dose of the vaccine.
Lead author Julia Hippisley-Cox told USA TODAY the purpose of the study was to demonstrate any risks associated with the vaccine are substantially less than with the COVID-19 infection.
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The study not only looked at blood clots but also thrombocytopenia, which is a condition characterized by low platelet counts and CVST, which is blood clots in the brain. They also studied ischaemic stroke, which is when a a blood clot or blockage cuts off the blood supply to the brain.
The study showed an increased risk of thrombocytopenia and blood clots in veins after a first dose of the AstraZeneca vaccine. For the Pfizer vaccine, researchers found a higher risk of blood clots in arteries and ischaemic stroke.
However, each of those risks more than doubled after COVID-19 infection in patients. For every 10 million people infected, there was be an extra 934 cases of thrombocytopenia, according to the study. They found only 107 extra cases after the first shot of the AstraZeneca jab.
For ischaemic strokes, the first Pfizer dose would result in only 143 extra cases but there would be about 1,699 extra cases for every 10 million people after infection.
Overall, the study showed while there is always a risk for blood clots, the risk is much lower with the first dose of a COVID-19 vaccine.
"The most difficult part of the study was undertaking the research during the vaccine roll out rather than waiting until it was complete," Hippisley-Cox told USA TODAY. "But our main motivation was to provide independent accurate assessment of risks to improve decision making."
Various studies have discovered increased health risks with COVID-19 infection compared to the vaccine. Most recently, the New England Journal of Medicine found a higher risk of myocarditis, occurring in 11 per 100,000 people infected with SARS-CoV-2. The infection also increased patients’ risk for arrhythmia, acute kidney injury, pulmonary embolism and more.
None of these increased risks were found in groups with the Pfizer vaccine.
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