For those of us treating patients with liver disease throughout the pandemic, we have anticipated evidence-based guidance regarding the contribution of specific liver disease phenotypes and immune suppression/transplantation on COVID-19 susceptibility and outcome. Now, data are emerging to help answer some of the major questions surrounding COVID-19 and the liver.
Does the Virus Itself Cause Liver Disease?
The answer to this question is still a bit unclear. Multiple early reports[1,2,3,4,5,6,7,8,9,10,11] stated that hospitalized patients with SARS-CoV-2 infection frequently had elevated values on liver biochemistry tests. For example, the reported incidence of elevated serum aspartate aminotransferase (AST) or alanine aminotransferase (ALT) levels ranged from 14% to 83%, yet the magnitude of enzyme elevation was generally reported to be mild and normalized as COVID-19 symptoms improved.
Unsurprisingly, patients with severe liver injury (defined as AST and ALT levels more than five times the upper limit of normal) were more likely to have a complicated clinical course, including having elevated inflammatory markers and requiring intensive care unit (ICU) admission, renal replacement therapy, and/or intubation. Currier and colleagues reported that patients with COVID-19 who had elevated AST and ALT levels had significantly higher odds of these same adverse outcomes and death.
This reflects the multifactorial pathogenesis of enzyme elevation, including a direct injurious effect of the virus on hepatocytes, cytokine or immune-mediated liver damage, drug hepatoxicity, or hypoxia and systemic inflammation.
Pellegrini and colleagues reported that 7% of patients infected with SARS-CoV-2 developed acute liver failure during their hospitalization, with a resulting mortality rate of 74%. Wagner and colleagues suggested that the pattern of peak elevated enzyme elevation was prognostic of severe clinical outcomes in hospitalized patients with COVID-19. Patients with a predominantly mixed pattern (AST/ALT and alkaline phosphatase elevations) had worse outcomes than those with a hepatocellular phenotype (isolated AST and/or ALT elevation).
Are Patients With Preexisting Chronic Liver Disease More Susceptible to Adverse Outcomes?
Early observations suggested that patients with chronic liver disease, such as cirrhosis, who acquire SARS-CoV-2 have high rates of hospitalization and mortality. However, it is unclear whether all such patients are affected or whether certain subgroups are at higher risk.
In results that they hoped would allow for better risk stratification and personalization of care, Kim and colleagues reported that patients with alcohol-related liver disease, decompensated cirrhosis, and hepatocellular carcinoma have the highest risk for all-cause mortality from COVID-19. Separate presentations at Digestive Disease Week 2021 confirmed that patients with preexisting liver disease had a threefold higher rate of mortality, thromboembolism, acute respiratory distress syndrome, and a severe COVID-19 disease course, and that patients with both COVID-19 and cirrhosis had significantly higher rates of mortality (18% vs 13%), ICU admission (46% vs 34%), and longer lengths of stay than those without cirrhosis.
Nonalcoholic fatty liver disease (NAFLD) is currently the most common chronic liver disease, and its impact on the course of SARS-CoV-2 infection (and vice versa) is controversial. However, metabolic risk factors, such as obesity, diabetes mellitus, and hypertension, are known to be associated with severe illness from COVID-19. It was also reported that hepatic steatosis was associated with worse outcomes in patients with liver injury and SARS-CoV-2 infection and that a higher proportion of patients with NAFLD required mechanical ventilation during their hospital course (47% vs 17%) and had increased mortality (41% vs 17%).
Do Immunosuppressed Patients Face Unique Risks From Infection?
Data from a limited case series, patient registries, and multicenter international studies have concluded that the clinical outcome of SARS-CoV-2 infection in adults with autoimmune hepatitis (AIH) was comparable to that noted in non-immunosuppressed persons. However, it has also been suggested that a more complicated relationship exists between this virus and autoimmunity because immunosuppression may actually protect against the inappropriate immune response, or cytokine storm, engendered during severe SARS-CoV-2 infection.
The complexity of this relationship is further illustrated by a report from Bril and colleagues that described a case of AIH that developed after a patient had received a COVID-19 vaccine. The authors were careful to state that a causal relationship between receipt of the vaccine and the onset of AIH cannot be proven.
What’s the Impact on Liver Transplant Recipients?
Findings are limited regarding clinical outcomes and disease severity of SARS-CoV-2 infection in liver transplant recipients, but initial reports raised concern for high rates of adverse outcomes.[16,17,18,19,20,21,22,23,24,25]
Tien and colleagues reported an increased risk for COVID-related death among liver transplant recipients. Separate international multicenter studies published in 2020 and 2021 found that liver transplant patients with COVID-19 had a significantly higher risk for hospitalization but no higher risk for mortality, thrombosis, or ICU requirement compared with patients with COVID-19 who had not undergone liver transplantation. Increased age and the presence of comorbidities were determinants of the severity of SARS-CoV-2 infection and of mortality among liver transplant recipients.
Clearly, more data are needed to address the influence of liver transplantation in patients with COVID-19; however, some risk/protective factors have been cited. For example, Belli and colleagues reported that the use of tacrolimus was associated with a better outcome. Conversely, baseline immunosuppression containing mycophenolate mofetil was an independent predictor of severe COVID-19 in liver transplant recipients.
Do COVID-19 Vaccines Work Differently in Patients With Liver Disease?
Unfortunately, we haven’t been able to address many of our patients’ questions related to vaccine efficacy, safety, and durability. Data are limited because immunocompromised patients were excluded from the phase 3 trials of the COVID-19 vaccines.
We also need greater clarity on the robustness of the response to these vaccines in liver transplant recipients. Rabinowich and colleagues evaluated humoral antibody responses after vaccination with the mRNA-based vaccine BNT162b2 (BioNTech/Pfizer) and confirmed lower immunogenicity in liver transplant recipients. Antibodies were detectable in only 48% of patients compared with 100% of healthy controls; in addition, antibody titers were significantly lower. Unfortunately, there are no data on the correlation of protection from SARS-CoV-2 with antibody titers.
Additional data will be required to assess vaccine effectiveness in protecting against severe COVID-19 as well as to determine the magnitude of humoral vaccine responses in recipients treated with high-dose steroids and mycophenolate mofetil. In addition, we eagerly await studies that determine whether booster doses are required.
What’s the Bottom Line?
In the face of the COVID-19 pandemic, our understanding of the impact on our patients remains a work in progress.
As we await more clarity, there are a few practical points of clinical relevance we take away from the literature, the recently released joint Statement on COVID-19 Vaccination in Solid Organ Transplant Recipients, and the American Association for the Study of Liver Diseases (AASLD) consensus statement. These suggest clinicians take the following steps:
When assessing patients with SARS-CoV-2 infection and elevated AST and ALT levels, the first objective is to rule out etiologies unrelated to COVID-19, specifically other viruses and drug-induced injury, as well as nonhepatic causes (eg, myositis, cardiac injury, ischemia).
Reduction in immunosuppression in SARS-CoV-2–infected patients with AIH should be considered carefully and generally undertaken only in those with severe illness.
Pretransplant SARS-CoV-2 vaccination is recommended for all liver transplant candidates and liver transplant recipients as well as their household members and caregivers, to reduce exposure for these patients, along with continued adherence to protective measures (masking and social distancing).
Continuation of a stable posttransplant immunosuppression regimen at the time of vaccination is recommended to avoid the risk for organ rejection until more comprehensive data are available.
For updated responses to the evolving guidelines, visit the AASLD’s resource center.
William F. Balistreri, MD, is the Dorothy M.M. Kersten Professor of Pediatrics; Director Emeritus, Pediatric Liver Care Center; Medical Director Emeritus, Liver Transplantation; and Professor, University of Cincinnati College of Medicine, Department of Pediatrics, Cincinnati Children’s Hospital Medical Center. He has served as director of the Division of Gastroenterology, Hepatology and Nutrition at Cincinnati Children’s for 25 years and frequently covers gastroenterology, liver, and nutrition-related topics for Medscape. Dr Balistreri is currently editor-in-chief of the Journal of Pediatrics, having previously served as editor-in-chief of several journals and textbooks. He also became the first pediatrician to act as president of the American Association for the Study of Liver Diseases. In his spare time, he coaches youth lacrosse.