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COVID-19 VACCINATION

HPC donors are considered high priorities for vaccination against COVID-19, and should be encouraged to proceed with vaccination as early as possible.

In principle the vaccination should take precedence over the donation schedule, with donor mobilisation and/or collection scheduled around vaccine administration to allow appropriate intervals between vaccination, G-CSF mobilisation and collection.

HPC or MNC donation after COVID-19 vaccination

The necessarily rapid implementation of COVID-19 vaccines makes it very important to compile comprehensive and accurate side effect data, and thus far these vaccines show a generally higher frequency, severity and duration of common side effects compared to most other vaccines.

G-CSF can cause very similar side effects, so an appropriate interval should be scheduled between vaccination and donor conditioning in order to minimise the risk of side effects combining or being attributed to the wrong injection.

In addition, reports have emerged of a rare vaccine-induced prothrombotic immune thrombocytopaenia (VIPIT; aka VATT, TTS or VITT) occurring after the AstraZeneca and Johnson & Johnson vaccines.  While published evidence for an adverse immune interaction with G-CSF is so far lacking, it would be prudent to avoid G-CSF within the most likely period of VIPIT onset following vaccination.  Current data as of May 2021 shows onset ranging from 4 to 29 days after vaccination, with the majority of cases presenting within 14 days.

Recommendations: it is recommended that G-CSF mobilisation should not commence until at least 24 hours after the complete resolution of vaccine side effects.  Given that side effects after COVID-19 vaccination often last one or two days, G-CSF mobilisation in a volunteer HPC(A) donor should be scheduled at least 3 days after a COVID-19 vaccine dose, and where possible a 7-day interval would nearly eliminate the risk of an unexpected delay to G-CSF mobilisation due to common vaccine side effects.  The same interval could also be applied to HPC(M) and MNC(A) donation.

For the AstraZeneca and Johnson & Johnson vaccines, and possibly other virus vector-based COVID-19 vaccines, a standard 21-day interval between vaccination and G-CSF mobilisation would cover the onset of nearly all VIPIT cases reported to date.

For any COVID-19 vaccine with a virus vector that is capable of replication, a standard 28-day interval may be considered in line with regulatory requirements for live/attenuated vaccines.

Where available, using a COVID-19 vaccine that does not use a virus vector will therefore minimise delays for HPC(A) donors.

COVID-19 vaccination after HPC or MNC donation

While there is no evidence so far on the effect of HPC or MNC donation on COVID-19 vaccine effectiveness, there is a theoretical concern that a reduced number of immune effector cells could have an adverse effect on the immune response to vaccination.

This concern is tempered by a number of known factors:

  1. HPC(A) donation does not typically reduce white blood cell numbers, due to G-CSF mobilisation.
  2. HPC(M) donation only causes a minimal reduction in WBC numbers.
  3. This theoretical concern is not specific to COVID-19 vaccines, and there is a lack of existing evidence for such an effect on other vaccines.

In contrast to HPC donation, MNC(A) donation does result in a significant reduction in total white blood cell numbers.  However, this is mitigated by the observation that peripheral WBC numbers after MNC(A) often remain as high or higher than pre-donation baseline levels due to natural mobilisation from peripheral pooling spaces.

Hence the physiological basis for this concern is limited, and provides little justification for a prolonged interval between MNC(A) and COVID-19 vaccination.

For the AstraZeneca, Johnson & Johnson and possibly other virus vector-based COVID-19 vaccines, there is a theoretical concern that immune stimulation following G-CSF mobilisation could increase the risk of VIPIT.  However, there is currently insufficient data to predict the safe post-HPC(A) interval in this situation, and perhaps the best strategy for donors for whom COVID-19 vaccination is indicated following HPC(A) collection will be to choose, where available, a vaccine that does not use a virus vector.

Recommendations: a COVID-19 vaccine should not be given until the donor has fully recovered from HPC or MNC donation.  COVID-19 vaccines that use a virus vector could incur VIPIT risk following G-CSF for an unknown period, and where available it would be prudent to use an alternative vaccine that does not use a virus vector in HPC(A) donors.

Summary tables:

AFTER VACCINATION WITH:

DONATION MAY BE SCHEDULED:

A COVID-19 vaccine with a virus vector capable of replication

·         HPC(A), HPC(M) & MNC(A) – collect no less than 28 days after vaccination.

A COVID-19 vaccine with a virus vector that is not capable of replication

·         HPC(A) – commence G-CSF no less than 21 days after vaccination.

·         HPC(M) & MNC(A) – collect no less than 3 days, and where possible 7 days, after vaccination.

All other COVID-19 vaccines

·         HPC(A) – commence G-CSF no less than 3 days, and where possible 7 days, after vaccination.

·         HPC(M) & MNC(A) – collect no less than 3 days, and where possible 7 days, after vaccination.

 

AFTER DONATING:

COVID-19 VACCINATION MAY BE GIVEN:

HPC(M)

MNC(A)

·         All vaccines: after the donor has fully recovered from the donation.

HPC(A)

·         Vaccines based on a virus vector: where available, an alternative vaccine should be used due to the theoretical risk of immune interaction with G-CSF.

·         Other vaccines:  after the donor has fully recovered from the donation.

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