According to a nationwide study in the UK, the Oxford-AstraZeneca vaccine, also known as Covishield, may be associated with a much smaller risk of developing a blood condition characterized by low platelet counts.
The increased risk of a condition known as idiopathic thrombocytopenic purpura (ITP) is estimated to be 11 per million doses, similar to figures seen in the flu, and measles, mumps and rubella (MMR) vaccines, the researchers said.
Low numbers of platelets — blood cells that help stop blood loss when vessels are damaged — may cause no symptoms or increase the risk of bleeding or, in some cases, clots, he said. said.
The team, led by researchers from the University of Edinburgh in the UK, noted that people most at risk from ITP are older – mean age of 69 years – and have at least one underlying chronic health problem such as coronary heart disease, diabetes or chronic disease. Kidney disease.
The researchers were unable to establish a definitive link between other types of clots because of the very small number of cases in the vaccinated people involved in the study – including a rare form called cerebral venous sinus thrombosis, or CVST.
The study of 5.4 million people in Scotland, of whom 2.5 million received their first vaccine dose, is the first analysis of the incidence of ITP, clotting and bleeding after vaccination in a whole country.
The authors of the study, published Wednesday in the journal Nature Medicine, emphasized that the likelihood of developing ITP after receiving the vaccine is less than the risk of developing it due to COVID-19.
He noted that the rare risk should not preclude the roll out of the vaccine program.
The same risk of ITP was not found for the Pfizer-BioNTech vaccine. Other vaccines were not included in the study.
The researchers analyzed a dataset as part of the EAVE II project, which uses anonymized linked patient data to track pandemics and vaccine roll out in real time.
They examined data up to April 14, 2021, for people in Scotland who had received their first dose of any vaccine.
To this date, more than 1.7 million had the Oxford-AstraZeneca jab and some 800,000 had a Pfizer-BioNTech vaccine dose.
Experts recommend that those receiving the Oxford-AstraZeneca vaccine should be exposed to a moderately increased risk of ITP, but also emphasize that the risk of developing these disorders from COVID-19 is potentially very high.
The UK’s Medical and Healthcare products Regulatory Agency (MHRA) reported low platelet counts in combination with blood clots following vaccination with AstraZeneca vaccine, estimated to occur at a rate of approximately 13 per million first doses.
Researchers including the universities of Strathclyde, Aberdeen, Glasgow, Oxford, Swansea and St Andrews also looked at health records dating back to September 2019 to check for any past issues with ITP, clotting or bleeding disorders.
The data was then compared with those who had yet to be vaccinated to determine whether any clotting events were out, which would have been expected pre-pandemic.
The analysis indicated that there was a slight increase in ITP in the second week after vaccination for those receiving the AstraZeneca vaccine and possibly an increased risk of arterial clots and bleeding events.
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