Based on our preliminary data, we would discourage single dose vaccines in immunocompromised individuals. (<0.40 U/ml), suboptimal (0.40C250 U/ml) and adequate (>250 U/ml). Of the 62 patients who had LT, antibody levels were undetectable in 11 patients and suboptimal (median titer 17.6, range 0.47C212 U/ml) in 27 patients. Among 79 patients with cirrhosis, 3 had undetectable antibody levels and 15 had suboptimal (median titer 41.3, range 0.49C221 U/L) antibody responses. Of the 92 patients without cirrhosis, 4 had undetectable antibody levels and 19 had suboptimal (median titer 95.5, range 4.9C234 U/L) antibody responses. Liver transplantation, use of 2 or more immunosuppression medications and vaccination with a single dose of ATV the Johnson & Johnson vaccine were associated with poor immune response on multivariable analysis. No patient had any serious adverse events. Conclusions Poor antibody responses after SARS-CoV-2 vaccination were seen in 61% of LT recipients and 24% of those with CLD. Lay summary The clinical efficacy of COVID-19 vaccines in immunocompromised patients is unknown. We performed a prospective study to evaluate immune responses to COVID-19 vaccines (Moderna, Pfizer or Johnson & Johnson) in 62 liver transplant recipients, AB05831 79 patients with cirrhosis and 92 with chronic liver diseases without cirrhosis. We found that 17.8% of liver transplant recipients, 3.8% of those with cirrhosis and 4.3% of those with chronic liver diseases without cirrhosis had undetectable antibody levels. In AB05831 total, 61.3% of liver transplant recipients and 24% of those with chronic liver diseases (with or without cirrhosis) had poor antibody responses (undetectable or suboptimal). Liver transplantation, use of immunosuppressive medications and vaccination with a single dose of Johnson & Johnson vaccine were associated with poor antibody responses when adjusted for other factors. Keywords: mRNA vaccine, SARS-CoV-2, liver transplant, cirrhosis, immunocompromised Graphical abstract Open in a separate window Introduction Patients with chronic liver disease and cirrhosis have worse outcomes from COVID-19 compared to those without liver disease.[1], [2], [3] Therefore, liver societies have recommended vaccination against SARS-CoV-2 for all patients with chronic liver diseases. Although the data on the outcomes of liver transplant recipients with COVID-19 are inconsistent, there is a definite trend towards higher mortality risks in transplant recipients.4 , 5 Liver transplant recipients or other immunocompromised patients were not included in the registration trials of mRNA vaccine studies for SARS-CoV-2. Although the clinical efficacy of COVID-19 vaccine in immunocompromised patients is unknown, many societies have recommended vaccination of this highly vulnerable patient population.[6], [7], [8], [9] It has been suggested, based on circumstantial evidence, that it is prudent to vaccinate immunocompromised patients since the benefits outweigh AB05831 the risks.10 , 11 However, a recent study reported that only 17% of organ transplant recipients developed detectable antibodies to the SARS-CoV-2 spike protein after the first dose of mRNA vaccines.12 Lower immune response was anticipated since humoral immunity is critical for antibody response after vaccination, but the response seen after the first dose was disappointingly low. We hypothesized that liver transplant recipients and those with advanced liver disease will have suboptimal response to SARS-CoV-2 vaccines. To test this hypothesis, in this ongoing prospective study, we assessed antibody responses 4 weeks after the 2nd dose of mRNA vaccines or after the single dose of Johnson & Johnson vaccine in liver transplant recipients and in those with chronic liver diseases with or without cirrhosis. Patients and methods In this prospective study, all adult patients (>18 years) with established chronic liver disease or those who received liver transplantation were eligible for the study..