Association between chronic hepatitis B infection and COVID-19 outcomes: A Korean nationwide cohort study.

<h4>Background/aims</h4>We measured the association between underlying chronic hepatitis B (CHB) and antiviral use with infection rates among patients who underwent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing.<h4>Methods</h4>In total, 204,418 patients who were tested for SARS-CoV-2 between January and June 2020 were included. For each case patient (n = 7,723) with a positive SARS-CoV-2 test, random controls (n = 46,231) were selected from the target population who had been exposed to someone with coronavirus disease 2019 (COVID-19) but had a negative SARS-CoV-2 test result. We merged claim-based data from the Korean National Health Insurance Service database collected. Primary endpoints were SARS-CoV-2 infection and severe clinical outcomes of COVID-19.<h4>Results</h4>The proportion of underlying CHB was lower in COVID-19 positive patients (n = 267, 3.5%) than in COVID-19 negative controls (n = 2482, 5.4%). Underlying CHB was associated with a lower SARS-CoV-2 positivity rate, after adjusting for comorbidities (adjusted odds ratio [aOR] 0.65; 95% confidence interval [CI], 0.57-0.74). Among patients with confirmed COVID-19, underlying CHB tended to confer a 66% greater risk of severe clinical outcomes of COVID-19, although this value was statistically insignificant. Antiviral treatment including tenofovir and entecavir was associated with a reduced SARS-CoV-2 positivity rate (aOR 0.49; 95% CI, 0.37-0.66), while treatment was not associated with severe clinical outcomes of COVID-19.<h4>Conclusions</h4>Underlying CHB and antiviral agents including tenofovir decreased susceptibility to SARS-CoV-2 infection. HBV coinfection did not increase the risk of disease severity or lead to a worse prognosis in COVID-19.