The European Medicines Agency (EMA) has recommended granting a conditional marketing authorisation for Oxford-AstraZeneca COVID-19 Vaccine to prevent coronavirus disease 2019 (COVID-19) in people from 18 years of age and older with no upper age limit. WHO has similarly listed the Oxford-AstraZeneca vaccine for emergency use.
Recently, rare cases of severe thrombosis and thrombocytopenia, some presenting as mesenteric vein or cerebral vein/cerebral venous sinus thrombosis, have been reported in persons who had recently received COVID-19 Oxford-AstraZeneca vaccine, mostly occurring within 14 days after vaccination. The majority of reports involved women under 60, although some of this may reflect greater exposure of such individuals due to targeting of particular populations for vaccine campaigns in different Member States.
The Pharmacovigilance Risk Assessment Committee of the European Medicines Agency taking into account all available evidence and advice concluded that a causal relationship between vaccination with Vaxzevria and very rare cases of thrombosis together with thrombocytopenia, sometimes accompanied by bleeding, is plausible.
The reported thromboses with thrombocytopenia include venous thrombosis, also in unusual sites such as cerebral venous sinus thrombosis (where blood clots in the brain's venous sinuses prevent blood from draining out of the brain) and splanchnic vein thrombosis (which involves one or more veins in the abdomen), as well as arterial thrombosis. Although such side effects are very rare, the reported case numbers exceeded what is seen in the general population.
Based on the available data, no specific risk factors were identified. The product information for Vaxzevria has been updated accordingly, and specifies thrombosis in combination with thrombocytopenia as a new very rare side effect (occurring in less than 1 in 10,000 persons).
Both EMA and GAVCS clearly state that after reviewing the data, the benefits of Vaxzevria in preventing COVID-19 continue to outweigh the risks; and there are no recommended changes regarding the use of this vaccine.[^1]
Health care personnel should be alert to the signs and symptoms of thromboembolism and or thrombocytopenia. Those vaccinated should be instructed to seek immediate medical attention if they develop symptoms such as shortness of breath, chest pain, leg swelling, persistent abdominal pain following vaccination. Additionally, anyone with neurological symptoms including severe or persistent headaches and blurred vision after vaccination, or who experience skin bruising (petechia) beyond the site of vaccination after a few days, should seek prompt medical attention.