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BSI response to study on AstraZeneca/Oxford vaccine and rare bleeding disorder

9 June 2021

A new study published in Nature Medicine examines the development of very rare cases of an autoimmune bleeding disorder known as idiopathic thrombocytopenic purpura (ITP) in vaccinated individuals in Scotland after receiving the first dose of the AstraZeneca/Oxford vaccine.

In response the British Society for Immunology has issued the following statement.


Dr Doug Brown, Chief Executive of the British Society for Immunology said:

“This study investigates real-world data of all vaccinated individuals in Scotland up until 14 April 2021 and examines the association between receiving the first dose of the AstraZeneca/Oxford and Pfizer/BioNTech vaccines and potential rare adverse effects related to clotting and bleeding disorders. The paper suggests a possible link between the AstraZeneca/Oxford vaccine and the development of very rare cases of idiopathic thrombocytopenic purpura (ITP), an autoimmune disorder characterised by low platelet counts.

“The occurrence of ITP after the first dose of the AstraZeneca/Oxford vaccine appears to be extremely rare – around one in 100,000 – and, as with other potential side effects of the COVID-19 vaccines, this risk remains far lower than the risks of serious health effects associated with COVID-19.

“It is important to note the limitations of the study, including the stage of the vaccination programme at the point of analysis (some individuals had received the second dose of the vaccine and few young people had been vaccinated), limited access to hospital medication records and the difficulty of ITP diagnosis. We therefore need to gather and analyse more robust data before we can know whether the AstraZeneca/Oxford vaccine induces this specific disorder.

“All the approved COVID-19 vaccines in the UK have been through rigorous clinical trials to ensure their safety and continue to be closely monitored during the rollout by the UK regulator, the Medicines and Healthcare products Regulatory Agency (MHRA). Vaccination is the safest and most effective way to protect yourself from falling ill with COVID-19 and we continue to encourage people to accept the offer of both doses of the vaccine.”


Read the full paper here. Simpson et al. 2021 First-dose ChAdOx1 and BNT162b2 COVID-19 vaccines and thrombocytopenic, thromboembolic and hemorrhagic events in Scotland. Nat Med doi.org/10.1038/s41591-021-01408-4