Exploring the Impact of COVID-19 Vaccination on Patients Taking Clozapine

Individuals with serious mental illness (SMI) are recognized to be among the highest risk patients to experience more severe symptoms of COVID-19, not only due to poor baseline health and associated disparity, but also due to medications prescribed to manage their illness that are known to compromise immunity even further. Clozapine, a gold standard antipsychotic used in the treatment for refractory schizophrenia, is considered to be the antipsychotic with the greatest risk of compromising immunity due to its potential to cause blood dyscrasia, including leukopenia and rarely, but potentially, agranulocytosis. The objective of this study is to determine if there is any potential hematological consequence for the use of COVID-19 messenger ribonucleic acid (mRNA) vaccines or the impact of active severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in patients receiving clozapine therapy. Since there is controversy over the rate of vaccine hesitancy in patients with SMI, we also examined the rate of vaccine acceptance in our subject population.

This study was a retrospective chart review conducted at a 160-bed state psychiatric inpatient hospital in upstate New York evaluating the impact of COVID-19 vaccination, SARS-CoV-2 infection, and vaccine acceptance in patients prescribed clozapine.

Both the administration of COVID-19 mRNA vaccines and SARS-CoV-2 infection did not appear to significantly influence the hematologic values that are monitored by the United States (US) Food and Drug Administration (FDA) to ensure safe use of clozapine. When offered vaccination, most patients hospitalized for SMI were willing to accept it.

With the likelihood of COVID-19 mRNA vaccinations becoming a recommended routine vaccination, requiring periodic boosters, patients receiving clozapine therapy have been observed to not be at higher risk of adverse hematological consequences when the mRNA vaccine is administered. Furthermore, inpatient psychiatry settings should be considered an optimal site of vaccination to improve vaccination efforts in our communities.