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 4 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, precautions and contraindications related to thrombocytopenia and coagulation disorders.
Benefits and risks of vaccination
The Joint Committee on Vaccination and Immunisation (JCVI) assessed benefits of COVID-19 vaccination using AstraZeneca against the risk of infection. They state 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 have issued a statement supporting JCVI advice on choice of vaccine for people aged under 40 years. The MHRA states the balance of benefits and risks is very favourable for older people but is more finely balanced for younger people and advise this evolving evidence should be taken into account when considering use of the vaccine.
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).
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:
Aged 40 years and over 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 39 and healthy
It is preferable for people in this age group to have a vaccine other than AstraZeneca. On 7th May 2021 JCVI advised alternative vaccines should be offered where possible and only where no substantial delay or barrier in access to vaccination would arise.
People in this group who are older, male, from certain minority ethnic backgrounds, experiencing socio-economic deprivation, or are obese are more at risk of serious consequences of COVID-19 and should be vaccinated.
Vaccination with any vaccine is always better than no vaccination, except where there are specific contraindications. Where AstraZeneca is the only practical option, the benefits of receiving this vaccine outweigh the risks and people in this age group should be offered it.
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 39 years who are health and social care workers, unpaid carers and family members of those who are immunosuppressed.
The only exception to receipt of a second dose of AstraZeneca COVI-19 vaccine are those people who have experienced major venous and/or arterial thrombosis occurring with thrombocytopenia following vaccination with any COVID-19 vaccine. This is listed as a specific contraindication in the AstraZeneca information for healthcare professionals.
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
- Updated to reflect new JCVI advice about use of AstraZeneca COVID-19 vaccine in people under 40 years of age.
- 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.