Oxford-AstraZeneca Vaccine Found to be Associated with Small Risk of Developing Rare Autoimmune Blood Disorder

June 9, 2021

A new study, published today in Nature, has reported the observance of a slightly increased risk of developing immune thrombocytopenic purpura (ITP) following inoculation with the Oxford-AstraZeneca vaccine. ITP is a rare autoimmune condition that results in excessive bruising or bleeding due to a decrease in the number of platelets in the blood.

The study looked at 2.53 million adults in Scotland who received their first doses of either the Oxford-AstraZeneca or Pfizer-BioNTech vaccine. There was no increased risk of blood disorders observed with the Pfizer-BioNTech vaccine. However, the Oxford-AstraZeneca vaccine risk of developing ITP was estimated at 1.13 cases per 100,000 people*. Risk factors found to be associated with developing post-vaccination ITP and other blood disorders included older age, male sex, smoking, and having other underlying conditions. 

* This very small risk is important but needs to be seen within the context of the overall benefits of receiving the vaccine for most people. ITP is still a very rare vaccine-induced adverse event and researchers plan to update their analysis as the vaccine program is extended to a larger demographic.

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