All COVID-19 vaccines currently licensed in the UK are non-live. Normally, no deferral period is applied after immunisation with non-live vaccines. However as the effects of the newly developed coronavirus vaccines on donor health and donation safety are not fully established yet, as a precautionary principle, a 14 to 28 day post vaccine deferral period, depending on the type of vaccine is recommended.
Immune thrombocytopenia (ITP) can occur after all types of Covid 19 vaccines. There have been a small number of reports of vaccine induced thrombosis and thrombocytopenia syndrome (VITTS), in people receiving virus vector based (non-replicating) coronavirus vaccine. VITTS patients have severe clinical symptoms whilst ITP may be sub-clinical and go unnoticed on symptoms alone. The incidence is unclear but may be similar to other vaccine induced ITP. Therefore a 14 day deferral period has been recommended after vaccination with mRNA vaccines.
GCSF administration carries a small risk of inflammation associated thrombosis and thrombocytopenia. There is a theoretical concern that GCSF could exacerbate the immune response related to VITTS. Headaches and abdominal pain are side effects of GCSF which are primary symptoms associated with cerebral venous thrombosis and splanchnic vein thrombosis respectively, due to VITTS. As a precautionary measure the post vaccination deferral period for bone marrow and PBSC donors receiving virus-vector-based (non-replicating virus) vaccines has been extended to 28 days, for donor protection. As the reported events are extremely rare, donors may be accepted less than 28 days after vaccination subject to a careful individualised risk assessment.
Consideration of checking a platelet count after vaccination to rule out thrombocytopenia is recommended. This could be included as a part of medical assessment if undertaken 14 days or more after vaccination. If less than 14 days between vaccination and medical assessment, or vaccination was given after medical assessment, additional Full Blood Count should be done before commencing GCSF/ general anaesthetic (frozen cells) and before commencing patient conditioning (for fresh cells).
For donors who have commenced GCSF, the vaccination (first or second dose) must be delayed at least until 72 hours after stem cell collection (both PBSC & Bone Marrow Donation). This is a precautionary advice to avoid vaccination when receiving GCSF and allow for post donation recovery period.
For donors vaccinated as part of a clinical trial or outside of the UK, the type of vaccine used should be established to determine the appropriate deferral period.
There may be new types of vaccine that become available, and it may not be known which type of vaccine was used for immunisation. In situations where information about vaccine type is missing or the vaccination is experimental, a four-week deferral period should be applied.
The British Society for Immunology has published an infographic to explain to the general public the different types of COVID-19 vaccines, including brand names, available in the UK, in other countries, and in clinical trials. See the following link: https://www.immunology.org/coronavirus/connect-coronavirus-public-engagement-resources/types-vaccines-for-covid-19
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