We would like to thank Mungmunpuntipantip and Wiwanitkit [1] for their response to our recent meta-analysis [2] on the possible confounding factors of vaccine recipients, including underlying medical conditions and prior coronavirus disease 2019 (COVID-19) infection. COVID-19 infection can cause not only gastrointestinal symptoms but also hepatic injury, including cholangitis and autoimmune hepatitis [3,4]. Therefore, vaccination is of paramount importance to prevent COVID-19 infection and its disease severity.

We agree that patients with more comorbidities may have different vaccine immunogenicity compared to healthy individuals. Table 1 shows the list of comorbidities among patients included in our analysis. No study provided individual data for the outcome of seroconversion regarding the presence of comorbidity. Importantly, non-alcoholic fatty liver disease, which may affect vaccine immunogenicity [5], is also associated with a higher risk of comorbidities, such as diabetes mellitus. Unlike the etiology of liver disease and cirrhosis status, wherein we used a prevalence of 80% as the cut-off for classification, the data for comorbidity were heterogenous and no cut-off could be drawn. Hence, we could not perform subgroup analysis with respect to each comorbidity. In addition, certain medications (e.g., antibiotics, angiotensin-converting enzyme inhibitors, histamine 2 receptor antagonists) may affect either the COVID-19 vaccine response [6] or disease severity [7,8]. However, drug data were lacking in the included studies.

Although prior history of COVID-19 infection was part of the exclusion criteria in our study, asymptomatic cases might have been enrolled, as the baseline levels of antibodies were measured. Timmermann et al. [9] found 2/120 asymptomatic patients with positive anti-nucleocapsid-immunoglobulin G antibodies, and these patients were excluded from subsequent analysis. A meta-analysis revealed that 0.25% of the tested general population were asymptomatic infections [10]. Nevertheless, this issue may not have a significant impact on our results due to a large sample size of 3,945 patients. It is noteworthy that vaccinated recipients, especially liver transplant patients, should still adhere to other infection prevention and control measures, such as social distancing [11].