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Possible link between AstraZeneca’s vaccine and rare blood clots, states EMA

EMA headquarter Amsterdam

The European Medicines Agency’s safety committee (PRAC) has concluded that unusual blood clots with low blood platelets should be listed as very rare side effects of Vaxzevria (formerly COVID-19 Vaccine AstraZeneca).

In reaching its conclusion, the committee took into consideration all currently available evidence, including the advice from an ad hoc expert group, it states in a press release.

Specific risk factors have not been confirmed

EMA is reminding healthcare professionals and people receiving the vaccine to remain aware of the possibility of very rare cases of blood clots combined with low levels of blood platelets occurring within 2 weeks of vaccination. So far, most of the cases reported have occurred in women under 60 years of age within 2 weeks of vaccination. Based on the currently available evidence, specific risk factors have not been confirmed.

The PRAC noted that the blood clots occurred in veins in the brain (cerebral venous sinus thrombosis, CVST) and the abdomen (splanchnic vein thrombosis) and in arteries, together with low levels of blood platelets and sometimes bleeding.

The overall benefits of the vaccine in preventing COVID-19 outweigh the risks of side effects

However, COVID-19 is associated with a risk of hospitalization and death, stated EMA. “The reported combination of blood clots and low blood platelets is very rare, and the overall benefits of the vaccine in preventing COVID-19 outweigh the risks of side effects,” they stated in a press release.

PRAC has requested new studies

One plausible explanation for the combination of blood clots and low blood platelets is an immune response, leading to a condition similar to one seen sometimes in patients treated with heparin (heparin induced thrombocytopenia, HIT). The PRAC has requested new studies and amendments to ongoing ones to provide more information and will take any further actions necessary.

Photo of Vivaldi building, the headquarters of the European Medicines Agency, shortly before completion: Wikipedia