AstraZeneca COVID-19 vaccine and blood clots

The Medicines and Healthcare products Regulatory Agency (MHRA) has said the available evidence does not suggest that blood clots in veins (venous thromboembolism) are caused by the COVID-19 Vaccine AstraZeneca. This follows a detailed review of report cases as well as data from hospital admissions and GP records. This has been confirmed by the Government’s independent advisory group, the Commission on Human Medicines, whose expert scientists and clinicians have also reviewed the available data.

A further detailed review into five UK reports of a very rare and specific type of blood clot in the cerebral veins (sinus vein thrombosis) occurring together with lowered platelets (thrombocytopenia) is ongoing. This has been reported in less than 1 in a million people vaccinated so far in the UK and can also occur naturally – a causal association with the vaccine has not been established.

The MHRA’s advice remains that the benefits of being vaccinated continue to outweigh any risks and that the public should continue to get their vaccine when invited to do so.

The European Medicines Agency has concluded their review and stated that the benefits of vaccination still outweigh the risks despite a possible link to rare cerebral blood clots with low blood platelets. A review into whether the vaccine could be the cause of this rare type of cerebral blood clot alongside low blood platelets is ongoing and the EMA, working alongside the MHRA, will continue to investigate this.

Information for patients and the public

  • Thrombotic events in veins are common in the general population and have not previously been associated with vaccination.
  • From the millions of people already vaccinated with the AstraZeneca Vaccine, there is no evidence of an increased incidence of blood clots in veins (DVT) higher than that seen in the general population.   
  • There are no confirmed issues related to any batch of vaccine used across Europe, or the rest of the world. Additional testing has, and is, being conducted by AstraZeneca and independently by European health authorities and none of these re-tests have shown cause for concern.
  • The MHRA is advising, as a precautionary measure, that anyone vaccinated who develops a headache that lasts for more than 4 days after vaccination or if they develop any bruising beyond the site of vaccination after a few days, should seek medical attention.
  • Mild flu-like symptoms remain one of the most common side effects of any COVID-19 vaccine, including headache, chills and fever. These generally appear within a few hours and resolve within a day or two, and not everyone gets them.