Risk of blood clots with COVID-19 vaccination
Public Health England (PHE) has highlighted reports of a very rare condition involving blood clots and unusual bleeding after vaccination. The risk appears to be higher in people who have had the first dose of the AstraZeneca vaccine, is seen slightly more often in younger people, and tends to occur between 4 days and 2 weeks following vaccination. This is being actively monitored for all COVID-19 vaccines.
The AstraZeneca COVID-19 vaccine information for healthcare professionals has been updated to reflect special warnings and precautions related to thrombocytopenia and coagulation disorders.
Benefits and risks of vaccination
The Joint Committee on Vaccination and Immunisation (JCVI) has assessed the benefits of COVID-19 vaccination using AstraZeneca against the risk of infection. They state that there is currently a high level of uncertainty in estimates of the incidence of this extremely rare adverse event. However, available data suggest there may be a trend for increasing incidence of this adverse event with decreasing age.
Whilst the Medicines and Healthcare products Regulatory Agency (MHRA) is not recommending age restrictions in AstraZeneca COVID-19 vaccine use, they and the JCVI have issued advice on how to minimise risks. The JCVI advises that all individuals offered a COVID-19 vaccine should be fully informed about the benefits and risks of vaccination including information on the extremely rare thrombosis/thrombocytopenia adverse event, how to monitor for symptoms, and what action to take.
The European Medicines Agency has produced information outlining the benefits and risks of Vaxzevria (AstraZeneca COVID-19 vaccine).
NHS England has produced an FAQ document to address some of the operational questions arising.
Age group specific advice
The benefit and risk analysis from the MHRA and JCVI is outlined in a leaflet produced by PHE. The following actions are suggested:
Over 50 years of age or with underlying medical condition
People should still receive any of the available COVID-19 vaccines and should also complete the course with the same vaccine they had for the first dose.
Aged 30 to 50 and healthy
People in this age group should still receive any of the available COVID-19 vaccines and complete the course with the same vaccine they had for the first dose.
Aged 18 to 29 and healthy
On 7th April 2021 JCVI advised that it is preferable for people under 30 to have a vaccine other than AstraZeneca. If they choose to have another COVID-19 vaccine they may have to wait to be protected. However, they may wish to go ahead with the AstraZeneca COVID-19 vaccination after considering all the risks and benefits.
If people have already had a first dose of AstraZeneca COVID-19 vaccine without suffering any serious side effects they should complete the course. This includes people aged 18 to 29 years who are health and social care workers, unpaid carers and family members of those who are immunosuppressed.
What to do if symptoms occur
Seek urgent medical advice in specific circumstances
PHE advise that if any of the following occur from around 4 days to 4 weeks after vaccination people should seek medical advice urgently:
- a new, severe headache which is not helped by usual painkillers or is getting worse
- a headache which seems worse when lying down or bending over
- an unusual headache that may be accompanied by blurred vision, nausea and vomiting, difficulty with speech, weakness, drowsiness or seizures
- new, unexplained pinprick bruising or bleeding shortness of breath, chest pain, leg swelling or persistent abdominal pain
Diagnosing and managing COVID-19 vaccine associated clotting disorders
A detailed case review is ongoing jointly by the MHRA, PHE and the Expert Haematology Panel. PHE has produced a page collating relevant national guidance.
The Royal College of General Practitioners has produced primary care guidance for management of suspected thromboembolism with thrombocytopenia after COVID-19 vaccination.
Guidance on vaccine induced thrombosis and thrombocytopenia (VITT) has also been produced by the British Society for Haematology (BSH) Expert Haematology Panel. It outlines factors associated with unlikely, possible, probable and definite cases together with recommendations for management. Details of how to report cases is also provided.
The Royal College of Emergency Medicine has produced a decision pathway on the management of patients presenting to the Emergency Department or Acute Medicine with symptoms of VITT.
People who have previously had VITT may present with recurrent symptoms and need to be monitored closely. The BSH have produced a triage policy for patients with previous VITT.
Reporting adverse events
Reporting suspected COVID-19 vaccine side effects, and potential product defects or counterfeit products
- Added reference to EMA information outlining benefits and risks of Vaxzevria (AstraZeneca COVID-19 vacccine).
- Added section on diagnosing and managing COVID-19 vaccine associated clotting disorders
- Added reference to NHS England FAQ document.