People who receive AstraZeneca's COVID-19 vaccine have a slightly increased risk of bleeding problems, according to a study published June 9 in Nature Medicine.
Researchers observed adults in Scotland who received their first doses of the COVID-19 vaccine developed by either AstraZeneca or Pfizer. Of the 2.53 million people they studied, 1.7 million received AstraZeneca's vaccine.
For Pfizer's vaccine, there was no increased risk of blood disorders. AstraZeneca's vaccine was linked to a slightly increased risk of immune thrombocytopenic purpura, a disorder that can cause serious bleeding in some cases. The study estimated the risk was 1.13 cases per 100,000 people receiving their first AstraZeneca vaccine dose, up to 27 days post-vaccination.
The study authors said immune thrombocytopenic purpura is treatable, and none of the people in the study who developed the disorder died from it. Since COVID-19 is much more likely to lead to the disorder than AstraZeneca's vaccine is, they said the benefits of getting the shot outweigh the slight risk.
The authors also said "alternative vaccines for individuals at low COVID-19 risk might be warranted when supply allows."