Myocarditis After Clozapine Initiation and mRNA SARS-CoV-2 Vaccination

A Rapid Review of the Effects of the COVID-19 Vaccine Among Individuals Taking Clozapine

BACKGROUND

The COVID-19 pandemic prompted the rapid development of vaccines to combat the virus. Several COVID-19 vaccines have proven effective in preventing infection, hospitalization, and death. Vaccination has been especially recommended for vulnerable populations, such as individuals with psychiatric illnesses who face increased risks due to comorbidities and socioeconomic factors. This rapid review identifies and analyzes the effects of COVID-19 vaccines among individuals taking clozapine.

METHODS

The review included articles from PubMed, OVID, Clinical Key, Web of Science, and Google Scholar, published between September 2020 and December 2023. Inclusion criteria were peer-reviewed journals, English language, patients on clozapine receiving a COVID-19 vaccine, and documented vaccine-related adverse effects.

RESULTS

Twelve articles were included, consisting of 8 case reports, 1 cross-sectional study, and 3 prospective observational studies, involving 298 subjects, with 9 subjects from case reports. After the first vaccine dose, 27 of 248 subjects experienced adverse effects, with 1 case report advising a temporary halt and dose reduction of clozapine. The subject in this case was admitted in a delirious state 4 days after vaccination with repeated falls and urinary incontinence; active infectious and neurologic etiologies were ruled out. Second dose data were available for 261 subjects, with 31 reporting adverse effects. Adverse effects included hematological changes, delirious state, seizures, and fever.

CONCLUSIONS

The review suggests that individuals on clozapine receiving COVID-19 vaccines may experience adverse effects. Clozapine levels and immune system interactions should be monitored in these cases.

Vaccination and clozapine use: a systematic review and an analysis of the VAERS database

In the context of COVID-19 concerns related to the potential interactions between clozapine and vaccination arose. With the ultimate goal of deriving recommendations for clinical practice, we systematically reviewed the current evidence regarding altered vaccine effectiveness in clozapine-treated patients and safety aspects of vaccination, such as haematological changes and the impact of vaccines on clozapine blood levels, in clozapine-treated patients. A systematic PRISMA-conform literature search of four databases (PubMed, PsycINFO, EMBASE and Cochrane Library) complemented by a case-by-case analysis of the Vaccine Adverse Event Reporting System (VAERS) database was performed. We then systematically appraised the joint evidence and tried to derive recommendations for clinical practice. 14 records were included in this analysis. These records consisted of 5 original articles and 9 case reports. Among the original articles, two studies provided data on the association between clozapine use and antibody responses to vaccination, both indicating that clozapine use in schizophrenia may be associated with reduced levels of immunoglobulins. Additionally, three studies examined vaccine safety in clozapine-treated patients, with no clinically significant adverse effects directly attributable to the interplay between vaccinations and clozapine. VAERS Analysis encompassed 137 reports and showed no consistent evidence of an increased risk for clozapine blood level increases or adverse events. We found no evidence indicating that clozapine impairs the effectiveness of vaccines. Moreover, no serious safety concerns seem to apply when patients on clozapine are receiving vaccines. However, it is crucial to acknowledge that data on the interaction between clozapine and vaccines remain limited.

Outcome of COVID-19 mRNA Vaccination in Patients Treated With Clozapine WHO Previously Went Through SARS-COV-2 Infection

BACKGROUND

The outbreak of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic had multiple consequences for the health care system, especially for patients with mental illnesses. Schizophrenia patients particularly appear to have a higher risk of complications due to coronavirus-19 (COVID-19). Clozapine remains the gold standard for treatment-resistant schizophrenia (TRS). However, the COVID-19 pandemic had an important negative impact on clozapine treatment, mainly because of its administration protocol, which was very difficult to follow during the restrictions imposed in the pandemic, and its side effects in patients with COVID-19 infection. Vaccination is an effective method of avoiding SARS-CoV-2 infection or its severe complications, especially in susceptible populations. Data on adverse events after vaccination against COVID-19 are limited, both in the general population and in schizophrenia patients.

STUDY QUESTION

The study aimed to investigate the safety of COVID-19 vaccination in patients treated with clozapine for hematological parameters.

STUDY DESIGN

We conducted an analytical cross-sectional study between July 1, 2021, and June 30, 2022. We compared 2 groups of COVID-19 vaccinated patients who had previously experienced SARS-CoV-2 infection: The first group was treated with clozapine, whereas the second group was treated with other antipsychotics.

MEASURES AND OUTCOMES

The primary objective was to identify granulocytopenia, leukocytopenia, and lymphocytopenia. The results were measured after the second dose of the Pfizer-BioNTech vaccine.

RESULTS

This study included 100 patients. White blood cell count changes were limited to a few cases of mild granulocytopenia (8.16% in the clozapine group and 3.92% in the nonclozapine group, P = 0.37) with no cases of severe granulocytopenia or agranulocytosis.

CONCLUSIONS

As far as leukocyte counts are concerned, mRNA COVID-19 vaccination seems to be safe in patients treated with clozapine who previously had SARS-CoV-2 infection. Leukocyte changes had no clinical implications.