BackgroundLimited data is available on the risk of hepatitis B virus (HBV) reactivation in patients with resolved infection undergoing kidney transplantation. It is generally thought that this risk is negligible. ObjectivesTo evaluate the incidence of HBV reactivation in such patients, and the potential risk factors for reactivation. Study designRetrospective cohort study including 93 patients transplanted with a kidney between 1995 and 2007 who had evidence of resolved HBV infection (HBsAg negative, anti-HBc positive, anti-HBs positive or negative, and normal liver enzymes). HBV reactivation was defined as HBsAg reversion with HBV DNA>2000IU/mL. ResultsSix patients experienced HBsAg reversion followed by HBV reactivation, 3 within the first post-transplant year. Immunosuppression regimen was similar in patients with and without reactivation. Among patients with reactivation only one was positive for anti-HBs antibodies at time of transplantation; these were progressively lost before reactivation. The odds ratio for reactivation in patients without anti-HBs antibodies at transplantation compared to those with anti-HBs antibodies was 26 (95% CI [2.8–240.5], p=0.0012). In patients with anti-HBs antibody titer above 100IU/L, no reactivation was observed. ConclusionsReactivation rate of resolved hepatitis B is not negligible in patients without anti-HBs antibodies at transplantation. We suggest monitoring of liver tests and HBV serology including HBsAg and anti-HBs antibodies after transplantation as well as vaccination pre- and post-transplantation in all patients, including those with resolved hepatitis B, aiming at maintaining anti-HBs antibody level above 100IU/L.