Table 2.

Descriptions of the state variables

State variable	Descriptions
$S$	HBV or COVID-19 susceptible group
$C_P$	COVID-19 protected individuals
$H_P$	HBV protected individuals
$C_V$	COVID-19 vaccine group
$C_I$	Individuals who are infected with COVID-19
$H_A$	Acute HBV mono-infected individuals
$H_C$	Chronic HBV mono-infected individuals
$I_{\mathit{AC}}$	Co-infected with acute HBV infection
$I_{\mathit{CC}}$	Co-infected with chronic HBV infection
$C_R$	COVID-19 recovery individuals
$H_T$	HBV treatment individuals