Clozapine and COVID-19 Vaccination: Effects on blood levels and leukocytes. An observational cohort study

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.

Clozapine Serum Concentrations Are Disrupted by SARS-CoV-2 Vaccinations

This paper reports the case of a 27-year-old man with paranoid schizophrenia who was finally stabilized on clozapine medication. After vaccination against severe acute respiratory syndrome coronavirus 2, serum levels of clozapine increased. It is well established that immune responses can trigger cytokine cascades affecting drug metabolism, which, in the case of clozapine treatment, can lead to severe intoxication.

Schizophrenia and the COVID-19 pandemic: A narrative review from the biomedical perspective

The outbreak of the Coronavirus Disease 2019 (COVID-19) pandemic in 2020 caused a rapid worsening of global mental health. Patients with severe mental disorders, including schizophrenia, are at higher risk of being infected. The neuroinvasive potential of the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) has been confirmed. The aim of this article was to present a narrative and comprehensive review of multidimensional associations between schizophrenia and COVID-19 with special emphasis on common biological pathways. Online searches were performed in the PubMed database and covered the publication period until September 17, 2022. Search terms included "psychosis", "schizophrenia", "inflammation" and "COVID-19". Viewed as a neuroinflammatory state, schizophrenia shares several neurobiological mechanisms with the COVID-19. Environmental stress, common comorbidities of schizophrenia and adverse effects of antipsychotic treatment are associated with the higher severity and mortality of the COVID-19. Additionally, more frequent relapses of psychosis have been observed, and might be related to lower treatment adherence. In the context of clinical manifestation, higher level of negative symptoms has been identified among patients with schizophrenia during the pandemic. Improvements in mental health care policy and treatment adjustment are necessary to protect people with schizophrenia who are the population that is particularly vulnerable to the consequences of the COVID-19 pandemic. Future research will show if prenatal infection with the SARS-CoV-2 increases a risk of psychosis.

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.

Adverse Hematological Effects of COVID-19 Vaccination and Pathomechanisms of Low Acquired Immunity in Patients with Hematological Malignancies

The SARS-CoV-2 virus and the COVID-19 pandemic have spread across the world and severely impacted patients living with hematological conditions. Immunocompromised patients experience rapidly progressing symptoms following COVID-19 infection and are at high risk of death. In efforts to protect the vulnerable population, vaccination efforts have increased exponentially in the past 2 years. Although COVID-19 vaccination is safe and effective, mild to moderate side effects such as headache, fatigue, and soreness at the injection site have been reported. In addition, there are reports of rare side effects, including anaphylaxis, thrombosis with thrombocytopenia syndrome, Guillain-Barré Syndrome, myocarditis, and pericarditis after vaccination. Further, hematological abnormalities and a very low and transient response in patients with hematological conditions after vaccination raise concerns. The objective of this review is to first briefly discuss the hematological adverse effects associated with COVID-19 infection in general populations followed by critically analyzing the side effects and pathomechanisms of COVID-19 vaccination in immunocompromised patients with hematological and solid malignancies. We reviewed the published literature, with a focus on hematological abnormalities associated with COVID-19 infection followed by the hematological side effects of COVID-19 vaccination, and the mechanisms by which complications can occur. We extend this discussion to include the viability of vaccination efforts within immune-compromised patients. The primary aim is to provide clinicians with critical hematologic information on COVID-19 vaccination so that they can make informed decisions on how to protect their at-risk patients. The secondary goal is to clarify the adverse hematological effects associated with infection and vaccination within the general population to support continued vaccination within this group. There is a clear need to protect patients with hematological conditions from infection and modulate vaccine programs and procedures for these patients.

COVID-19 Vaccines and the Virus: Impact on Drug Metabolism and Pharmacokinetics

This article reports on an American Society of Pharmacology and Therapeutics, Division of Drug Metabolism and Disposition symposium held at Experimental Biology on April 2, 2022, in Philadelphia. As of July 2022, over 500 million people have been infected with SARS-CoV-2 (the virus causing COVID-19) and over 12 billion vaccine doses have been administered. Clinically significant interactions between viral infections and hepatic drug metabolism were first recognized over 40 years ago during a cluster of pediatric theophylline toxicity cases attributed to reduced hepatic drug metabolism amid an influenza B outbreak. Today, a substantive body of research supports that the activated innate immune response generally decreases hepatic cytochrome P450 activity. The interactions extend to drug transporters and other organs and have the potential to impact drug absorption, distribution, metabolism, and excretion (ADME). Based on this knowledge, altered ADME is predicted with SARS-CoV-2 infection or vaccination. The report begins with a clinical case exploring the possibility of SARS-CoV-2 vaccination increasing clozapine levels. This is followed by discussions of how SARS-CoV-2 infection or vaccines alter the metabolism and disposition of complex drugs, such as nanoparticles and biologics and small molecule therapies. The review concludes with a discussion of the effects of viral infections on placental amino acid transport and their potential to impact fetal development. The session improved our understanding of the impact of emerging viral infections and vaccine technologies on drug metabolism and disposition, which will help mitigate drug toxicity and improve drug and vaccine safety and effectiveness. SIGNIFICANCE STATEMENT: Altered pharmacokinetics of small molecule and complex molecule drugs and fetal brain distribution of amino acids following SARS-CoV-2 infection or immunization are possible. The proposed mechanisms involve decreased liver cytochrome P450 metabolism of small molecules, enhanced innate immune system metabolism of complex molecules, and altered placental and fetal blood-brain barrier amino acid transport, respectively. Future research is needed to understand the effects of these interactions on adverse drug responses, drug and vaccine safety, and effectiveness and fetal neurodevelopment.

Clozapine Therapy and COVID-19: A Systematic Review of the Prevalence Rates, Health Outcomes, Hematological Markers, and Patient Perspectives

BACKGROUND/OBJECTIVES

There have been concerns that clozapine treatment may undermine the capacity of the body to fight infection and increase the vulnerability to contracting COVID-19. This review of recent cohort studies investigated (1) whether people with a severe psychiatric disorder are at increased risk of COVID-19 and complications, (2) the immunological response of clozapine-users who contract COVID-19, and (3) patients' perspectives on COVID-19 and the pandemic response.

METHODS

A systematic search of EMBASE, Medline, Pubmed, and PsycINFO databases using PRISMA guidelines using "COVID-19", "clozapine", and "vaccination" terms.

RESULTS

18 studies (out of 330 identified) met all criteria (N = 119 054 including 8045 on clozapine). There was no strong evidence that clozapine users may be at increased risk of contracting COVID-19 or developing complications after adjusting for medical comorbidities. Hematological studies showed temporary reductions in neutrophils in COVID-19-positive patients and vaccination suggesting a clozapine effect in defence against infection. Vaccination studies did not report major adverse effects. Increased plasma levels of clozapine and neutropenia however point to COVID-19-related interference of clozapine metabolism. Patient surveys reported limited impact on mental health and positive attitudes regarding pandemic response.

CONCLUSION

This review did not find compelling evidence that the immune system of clozapine users put them at risk of COVID-19 and further complications. Evidence of drug-infection interactions however points to the importance of adhering to consensus guidelines about clozapine therapy during the pandemic. More evidence using longitudinal designs is required to examine the longer-term effects of COVID-19 and vaccination in this vulnerable population.

Attitudes towards Vaccines, Intent to Vaccinate and the Relationship with COVID-19 Vaccination Rates in Individuals with Schizophrenia

Schizophrenia patients are at high risk of developing severe COVID-19 outcomes but recent evidence suggests that they are under-vaccinated. This study explored the role of potential attitudinal barriers by comparing schizophrenia patients with participants from the general population regarding COVID-19 vaccination rates, general attitudes towards vaccines, and willingness to take a COVID-19 vaccine. We conducted a cross-sectional study between April 2021 and October 2021. A total of 100 people with schizophrenia and 72 nonclinical controls were recruited. In our study, individuals with schizophrenia were under-vaccinated, despite similar general attitudes towards vaccination and higher willingness to be vaccinated against COVID-19 compared to nonclinical participants. In patients, negative attitudes toward vaccines were related to higher levels of negative psychotic symptoms and higher levels of paranoid ideation. As a whole, participants with more negative attitudes towards vaccines were less likely to be vaccinated against COVID-19 and had lower levels of trust in institutions. Vaccine hesitancy does not appear to be a major barrier for COVID-19 vaccine uptake amongst people with schizophrenia. This study suggests that disparities in COVID-19 vaccination rates in schizophrenia do not seem related to attitudinal but rather structural barriers.