Vaccine-induced Thrombocytopenia and Thrombosis (VITT)


Barts Health: This is a live document and will be updated frequently as further information comes to light.

“Astra Zeneca vaccine” in this document refers to the CHaDOx1 nCov-19 vaccine.

There are currently no robust data to inform management of this condition. In the absence of evidence, this is advice based on our experience and that of the national expert haematology MDT in managing this and similar conditions and the theoretical risks and benefits of interventions. The national guidance on the signs, symptoms and management of this condition are available via the following link:

https://b-s-h.org.uk/about-us/news/guidance-produced-by-the-expert-haematology-panel-ehp-focussed-on-vaccine-induced-thrombosis-and-thrombocytopenia-vitt/

To date we have seen very few confirmed cases at Barts Health of the rare vaccine-induced thrombocytopenia and thrombosis syndrome (VITT) all occurring after the Astra Zeneca vaccine. In contrast, thrombotic complications have been observed in COVID-19 infection in 20% of severely affected, 5% of moderately affected and 1% of mildly affected patients and are a major cause of death. 

The ultimate choice as to whether a person accepts a vaccination is their own and decisions are likely to be influenced by many factors. We hope this information will be helpful to you and your patients to help make that decision. 

  • GROUP 1:
    • Patients with a prior history or family history of thrombosis or a thrombophilia (including heritable thrombophilia, the antiphospholipid syndrome and a history of non-vaccine-associated cerebral venous sinus thrombosis)
    • who are on anticoagulants or have stopped taking anticoagulants on medical advice
    • who are unvaccinated

The value of vaccination in preventing death and blood clots from COVID-19 infection outweighs the estimated risk of VITT in this group. We encourage these patients to receive their vaccinations in line with the current government advice, including the Astra Zeneca vaccine if it is offered.  

This advice is in keeping with the Green Book* and the national VITT MDT expert panel. We recognise there is a discrepancy with the Astra Zeneca vaccine summary of product characteristics which is being addressed by the national expert MDT.

  • GROUP 2:
    • Patients with a prior history or family history of thrombosis or a thrombophilia (including heritable thrombophilia or the antiphospholipid syndrome)
    • who are on anticoagulants or have stopped taking anticoagulants on medical advice
    • who have had a single Astra Zeneca vaccine

It has not been clinically proven that using different vaccines provides an adequate immune response to the virus. We encourage all patients to have 2 doses of the same manufacturer.

The value of vaccination outweighs the estimated risk of VITT at this time and we encourage patients in this group to receive their vaccinations in line with the current government advice.  

This syndrome has not been encountered in anyone following a second dose, though this must be interpreted in the context of relatively low rate of second vaccination so far. 

In patients in whom a second vaccination is not imminent, please recheck this site and government guidance nearer to the time in case developments in our understanding of VITT lead to a change in policy.

This advice is in keeping with the Green Book* and the national VITT MDT expert panel. We recognise there is a discrepancy with the Astra Zeneca vaccine summary of product characteristics which is being addressed by the national expert MDT.

  • GROUP 3: Patients with a pre-existing low platelet count (thrombocytopenia) including immune thrombocytopenia

The value of vaccination in preventing death and blood clots from COVID-19 infection outweighs the estimated risk of VITT in this group.

In the subset of this group with immune thrombocytopenia (ITP) we know that any medication, vaccination or illness can precipitate a flare of the disease, however the value of vaccination still outweighs the risk. ITP patients who develop symptoms or signs of bleeding or excess bruising at any time are encouraged to seek medical help from their ITP service.  

  • GROUP 4: Patients in whom there is a clinical suspicion of vaccine-associated thrombosis or thrombocytopenia

Please note that symptoms associated with VITT have included:

  • Classical symptoms of deep vein thrombosis, pulmonary embolism, coronary syndromes and limb ischaemia
  • Persistent or severe headache, seizures, focal neurology in the event of cerebral venous sinus thrombosis
  • Abdominal pain in the event of intra-abdominal thrombosis
  • New onset bleeding, bruising or petechiae

In patients in whom there is a high clinical suspicion of thrombosis or symptomatic thrombocytopenia referral to secondary care should occur the same day, in keeping with existing pathways for the management of thrombosis and bleeding. Community blood tests should not delay this.

 

A community full blood count with a same-day turnaround can be used to inform clinical decisions in primary care, especially when the prior clinical suspicion of thrombosis or thrombocytopenia is low. 

 

  • GROUP 5: Patients who had had a thrombosis with onset of symptoms in 5-28 days of the Astra Zeneca vaccination

These patients will be followed up by the Barts Health haematology team. Please urgently refer any patient without haematology follow-up via e-referrals/ CRS communicate and ensure that the patient continues their anticoagulation until they are seen in clinic. They should not be offered a second Astra Zeneca vaccination until the risk has been assessed in clinic.

  • GROUP 6: Patients who had had a thrombosis with onset of symptoms <5 days or >28days following the Astra Zeneca vaccination

These patients will be followed up by the Barts Health haematology team. Please send an e-referral for any patient without haematology follow-up and ensure that the patient continues their anticoagulation until they are seen in clinic. These patients can be offered the second Astra Zeneca vaccination when it is due, in line with government guidance.

  • GROUP 7: Patients who have a history of heparin-induced thrombocytopenia (HIT)

According to the latest version of the Green Book* patients with a history of HIT should not receive the Astra Zeneca vaccine. No cases have yet occurred in patients with a history of HIT, and this is likely to be a precautionary action in view of a similar proposed mechanism of disease underlying VITT and HIT. These patients are often coded on the East London Patient Record as having a heparin allergy.

*Green book link: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/978508/Green_book_chapter_16April2021.pdft