Two Patients with Schizophrenia Treated with Clozapine Developed Neutropenia After Receiving a COVID-19 Vaccine.

BACKGROUND: We observed two cases of patients with schizophrenia who were treated with clozapine (250mg/day and 275mg/day, respectively) and showed neutropenia after receiving a COVID-19 vaccine (BNT162b2). CASE PRESENTATION: Case 1 is a twenty-two year old woman with a diagnosis of schizophrenia. She enrolled in Clozaril® Patient Monitoring Service in 2017 and had been taking clozapine for 4 years. She received two doses of a COVID-19 vaccine and developed neutropenia (1850/mm3 (37.9% of white blood cell 4880/mm3)) 6 days after the second vaccination, but her neutropenia self-resolved naturally. Case 2 is a twenty year old woman with a diagnosis of schizophrenia. She enrolled in Clozaril® Patient Monitoring Service in 2020 and had been taking clozapine for 10 months. She received two doses of a COVID-19 vaccine and white blood cell and neutrocyte counts were below (3730/mm3 and 1440/mm3 (38.6%), respectively) the lower limits 3 days after the second vaccination. She had to discontinue clozapine according to the withdrawal definition (her neutrocyte count was <1500/mm3), and her neutropenia self-resolved naturally. CONCLUSION: Physicians need to have a strict follow-up protocol in place for patients after vaccination for COVID-19.