Clozapine treatment and COVID-19 vaccination


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Clozapine treatment and COVID-19 vaccination

Key messages:

  • Clozapine is NOT contraindicated with COVID-19 vaccines
  • Manufacturer does not anticipate any adverse effects of combining clozapine with COVID-19 vaccines based on experience with other vaccines
  • Limited clinical data on the use of the vaccines with medications

As GGC moves forward with the COVID-19 vaccination programme, patients on clozapine will start to be called to attend for their vaccine. Underlying health conditions increase the risk of morbidity and mortality from COVID-19; severe mental illness has been identified as a one of the main risk groups. Also within this group are “people on immunosuppression therapies sufficient to significantly increase risk of infection”, while clozapine is not an immunosuppressant, it may be regarded a risk due to the possibility of neutropenia.

Clozapine plasma levels

Patients may experience some signs of inflammation after vaccination and this response could in theory lead to increased clozapine plasma levels. It may therefore be recommended to monitor patients for symptoms of inflammation, such as fever or flu-like symptoms, and for possible signs of clozapine toxicity. If a patient shows fever or flu-like symptoms, a FBC must be taken immediately to exclude clozapine induced neutropenia or agranulocytosis.

Effect of vaccines on white cell count (WBC)

Vaccination could theoretically lead to reduced total WBC counts, with lymphocytes mainly accountable for the drop. The effect is probably not huge and will most likely only cause red results in patients who already have low WBC counts. The effect starts within 2 days after vaccination and may last for weeks, but any new red result that occurs after a month is unlikely to be caused by vaccination.

If a patient has a red result following vaccination clozapine should still be discontinued immediately and daily testing should be carried out until two ‘green’ blood results have been obtained. Any decision to restart clozapine should be discussed with the appropriate clozapine monitoring service.

For further advice please contact Leverndale Pharmacy on 211 6525.

Prescribing Management Group- Mental Health February 2021                                                                                                                             

Last reviewed: 22 December 2021

Next review: 01 June 2022

Approved By: Prescribing Management Group - Mental Health