ObjectiveTo investigate the main clinical influencing factors for the rate of active immune response to hepatitis B vaccine in adult hepatitis B recipients after liver transplantation. MethodsAnalysis was performed for the clinical follow-up data of 15 hepatitis B recipients after liver transplantation who received hepatitis B vaccine in Peking University International Hospital from May 2019 to November 2020, and all patients received liver transplantation at least 3 years before and had a CD4 level of 300-800 cells/u before vaccination. Each dose of vaccination was 40 μg recombinant hepatitis B vaccine (Saccharomyces cerevisiae), with a total of 4 injections at 0, 1, 6, and 8 months. Anti-HBs ≥100 mIU/L after four injections which lasted for 12 weeks without attenuation was considered successful response. Pearson correlation analysis and Kendall correlation analysis were used to investigate the correlation between CD4 level before vaccination and vaccine response rate; a linear regression analysis was used to investigate whether CD4 level before vaccination could predict the titer of anti-HBs after active vaccine immunization; a logistic regression analysis was used to investigate whether CD4 level before vaccination could predict vaccine response. ResultsOf all patients at week 12 of monitoring, 6 patients had response, among whom 1 had an anti-HBs level of ＞1000 mIU/L and 5 had an anti-HBs level of ≥100 mIU/L, and the antibody titer did not attenuate till week 16; the response rate of hepatitis B vaccine was 40%. The 6 patients with response had a mean CD4 level of ≥592 cells/u before vaccination, while the 9 patients without response had a mean CD4 level of ≤500 cells/u before vaccination. CD4 level before vaccination was strongly correlated with the response rate of hepatitis B vaccine (Pearson correlation analysis: r=0.767, P=0.001; Kendall correlation: r=0.717, P=0.001). ConclusionCD4 level before vaccination is a key clinical factor affecting the response rate of hepatitis B vaccine after liver transplantation.