In December 2019, the world was introduced to a new and formidable pathogen, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19). First identified in Wuhan, China, this highly transmissible and pathogenic virus quickly spread across continents, leading to a global pandemic. The disease spectrum of COVID-19 ranges from mild symptoms to severe cases necessitating hospitalization, with a notably higher risk of mortality among individuals with pre-existing health conditions.
In response to the urgent global health crisis, the scientific community prioritized the development of vaccines, leading to the expedited authorization of several candidates. Among these, the Pfizer-BioNTech, Oxford-AstraZeneca, and Moderna vaccines emerged as frontrunners, significantly reducing major adverse outcomes of COVID-19, such as hospitalizations, intensive care unit admissions, and death rates. The rapid deployment of these vaccines starting at the end of 2020 marked a pivotal moment in the fight against the pandemic, with reported side effects being rare and generally mild, underscoring the vaccines’ safety and tolerability.
However, with the widespread administration of the vaccines, reports of immune-mediated adverse events began to surface, including the first documented case of liver injury post-vaccination by Pfizer-BioNTech, as reported by Bril et al. Subsequent cases highlighted clinical and histological patterns akin to autoimmune hepatitis (AIH), with affected individuals responding positively to corticosteroid therapy. This raised concerns about the potential for vaccine-induced autoimmunity, particularly in susceptible individuals, leading to international collaborative efforts to investigate these incidents more thoroughly.
An extensive study involving 18 countries was initiated to gather data on patients who developed liver injury post-SARS-CoV-2 vaccination. This retrospective analysis, coordinated by Harran University Hospital in Şanlıurfa, adhered to ethical standards approved by local review boards. The study aimed to elucidate the clinical characteristics, treatment efficacy, and outcomes of these patients, providing critical insights into a relatively rare but concerning adverse effect.
Liver injury in this context was defined by specific criteria related to enzyme levels, with the injury categorized based on the R-value, reflecting the nature of the liver damage as hepatocellular, mixed, or cholestatic. The severity was further classified from mild to fatal, depending on enzyme levels, symptoms, and signs of liver failure. Comprehensive data collection encompassed a wide range of laboratory and serologic markers, including antibodies and viral serologies, to accurately diagnose and assess the extent of liver injury.
Statistical analysis employed sophisticated software and methodologies to ensure the reliability of findings, with various tests applied to compare and contrast the data among different patient groups. This rigorous approach aimed to identify significant patterns and outcomes, contributing valuable knowledge to the medical community and informing future vaccine development and safety monitoring practices.
The international collaboration and detailed investigation into vaccine-related liver injury underscore the commitment of the global health community to ensuring the safety of COVID-19 vaccines. While the benefits of vaccination against COVID-19 are undeniable, continuous monitoring of adverse events is essential to address potential concerns promptly and maintain public trust in vaccination programs. This study not only provides a framework for such efforts but also highlights the importance of global cooperation in tackling the challenges posed by the pandemic.
DISCUSSION – Hepatotoxicity Potential of SARS-CoV-2 Vaccines: Clinical Presentation, Management, and Prognosis
In a comprehensive study conducted by experienced hepatologists across Europe and the Americas, the clinical presentation, laboratory features, and prognosis of liver injury associated with SARS-CoV-2 vaccination have been thoroughly examined. The study sheds light on this rare but important issue, emphasizing the need for early recognition and appropriate management.
The study encompassed 87 patients who developed liver injury in the wake of receiving SARS-CoV-2 vaccines, with a focus on the Pfizer-BioNTech, Moderna, and Oxford-AstraZeneca formulations. While the overall outcomes of these cases were generally positive, there was one patient who experienced fulminant liver failure, ultimately necessitating a liver transplantation.
Liver injury in these cases predominantly exhibited hepatocellular characteristics and indicated immune-mediated hepatitis. Among the 44 patients who underwent a comprehensive laboratory and histological assessment, a staggering 77% met the criteria for probable or definite autoimmune hepatitis (AIH) as per the simplified AIH criteria. This observation is consistent with previously reported instances of post-SARS-CoV-2 vaccine-induced liver injury, most of which also displayed AIH features.
The exact mechanism underlying SARS-CoV-2 vaccine-induced liver injury remains unclear. However, both mRNA and viral vector vaccine formulations encode the SARS-CoV-2 spike (S) protein, which can stimulate innate immunity and lead to the production of proinflammatory cytokines and chemokines. Due to molecular similarities between the S protein and liver-specific proteins, an activated immune system may inadvertently target liver proteins. A recent study even revealed that anti-SARS-CoV-2 S protein antibodies reacted to human tissue antigens, causing significant increases in immune-mediated markers like ANA, anti-actin, and AMA.
Corticosteroid therapy emerged as a viable treatment option for many patients with immune-mediated liver injury. A significant proportion of individuals with this condition received corticosteroids in the study, and this treatment was generally well-tolerated with no severe side effects reported. Notably, corticosteroid therapy was more frequently administered to patients with severe hepatitis, potentially contributing to the prolonged time required for aminotransferase levels to normalize in these individuals.
Remarkably, one patient experienced liver failure attributed to SARS-CoV-2 vaccination, marking the first reported case requiring liver transplantation due to vaccine-induced liver failure. Another patient with severe hepatitis and hepatic encephalopathy was listed for transplantation but ultimately improved with plasma exchange and corticosteroid therapy. While most reports indicate a positive response to therapy, they also underscore the importance of recognizing the potential severity of liver injury following SARS-CoV-2 vaccination.
Distinguishing immune-mediated liver injury stemming from vaccination from new-onset or flare-ups of pre-existing AIH poses a challenge. Nonetheless, careful examination of clinical and histological data can provide valuable insights. For example, patients who exhibited advanced fibrosis were more likely to have AIH, and steroid response and long-term outcomes can also help differentiate between these conditions.
Determining causality can be complex, especially in cases with pre-existing conditions and concomitant medication. Some patients in the study experienced liver injury following vaccination despite being adherent to immunosuppressive therapy, making a spontaneous AIH flare unlikely. Furthermore, the rapid onset of symptoms shortly after vaccination in some cases suggests a causal link.
The study also addressed potential causative factors such as statin therapy and interferon therapy, both known to induce immune-mediated liver injury. However, re-introduction of these medications did not result in liver injury relapse, suggesting a low likelihood of causality. The use of acetaminophen and ibuprofen for post-vaccine symptoms was also examined, with no strong evidence of a direct link to liver injury.
Importantly, the study revealed that some patients experienced more severe liver injury following the second dose of the same vaccine type. This suggests caution should be exercised when considering re-exposure to the same vaccine type after SARS-CoV-2 vaccine-induced liver injury. Heterogeneous vaccination, involving different vaccine types for the first and second doses, has shown greater efficacy in previous studies.
In conclusion, this extensive international case series highlights the potential for hepatotoxicity associated with SARS-CoV-2 vaccines, including Pfizer-BioNTech, Moderna, and Oxford-AstraZeneca. While the clinical presentation is mainly hepatocellular and immune-mediated hepatitis, most cases had positive outcomes with spontaneous resolution and good steroid response. However, clinicians should remain vigilant as some patients may experience severe liver injury, emphasizing the importance of early recognition and appropriate management. The study’s findings ultimately underscore the overwhelming benefits of SARS-CoV-2 vaccination during the pandemic, despite these rare side effects.
REFERENCE LINK : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9348326/