| In addition to the development of the long-term complications, namely end-staged liver cirrhosis and hepatocellular carcinoma from hepatitis B virus (HBV) infection, there is another severe and potentially fatal complication from the disease i.e. HBV reactivation. Although HBV reactivation can sometimes occur spontaneously, it is quite often related to presence of triggering factors. Use of immunosuppressive therapies including chemotherapy, biologics, immunosuppressants in malignant conditions, autoimmune diseases and organ/ haematopoietic stem cell transplantations (HSCT) are the well-known precipitating factors. The consequence of HBV reactivation in these conditions is however largely preventable. Therefore, routine screening for HBV serology have been widely implemented particularly for patients with malignant conditions undergoing chemotherapy or biologics treatment. It is now recommended that all HBsAg positive patients undergoing immunosuppressive therapy should be prophylactically treated with anti-viral agents.
Over the recent few years, frequent occurrence of HBV reactivation in HBsAg negative/ anti-HBc positive patients receiving potent immunosuppressive therapy e.g. rituximab and HSCT have been observed. The strategy for prevention of HBV reactivation varies with different centres because of the lack of studies to examine the following aspects: 1) defining patients with high and low risk of HBV reactivation; 2) effectiveness of adopting prophylactic vs. pre-emptive antiviral treatment; 3) interval of HBV DNA monitoring; 4) duration of therapy after cessation of immunosuppressive therapy and 5) the protective role of anti-HBs. More studies to examine these outstanding issues are urgently required in the future.