Potential Protective Effect of Hepatitis B Immunity Against Diabetes Mellitus: A Retrospective Propensity-Matched Cohort Study.

: Hepatitis B virus (HBV) infection affects glucose metabolism and increases diabetes risk; HBV vaccination may reduce this risk. The role of HBV immunity in diabetes prevention among individuals without HBV infection is underexplored. This study aims to evaluate whether HBV immunity reduces diabetes risk in individuals without HBV infection. : This retrospective cohort study used de-identified electronic medical records from TriNetX. Adults with hepatitis B surface antibody (HBsAb) results without a history of HBV infection or diabetes were identified. Diabetes was defined on the basis of a diabetes diagnosis, diabetes medication use, or glycated hemoglobin ≥ 6.5%. Propensity score matching was conducted to balance demographics and comorbidities between groups. : The HBV-immunized group had a 15% lower diabetes risk than the HBV-unimmunized group (HR: 0.85 [0.84-0.87]). A dose-response effect was observed, with higher HBsAb levels showing a greater reduction in the risk of diabetes. HBsAb levels of ≥100 and ≥1000 mIU/mL were associated with 19% (HR: 0.81 [0.80-0.83]) and 43% (HR: 0.57 [0.54-0.60]) reductions in diabetes risk, respectively, compared with HBsAb < 10 mIU/mL. The reduced risk of diabetes was associated with age. Immunized individuals aged 18 to 44 years, 45 to 64 years, and ≥65 years had 20% (HR: 0.80 [0.78-0.82]), 11% (HR: 0.89 [0.87-0.92]), and 12% (HR: 0.88 [0.84-0.91]) lower diabetes risks, respectively, compared with unimmunized individuals. HBV immunity may be associated with a reduced risk of diabetes, suggesting broader HBV vaccination as a dual-benefit strategy for the prevention of hepatitis B and diabetes, especially in regions with a high prevalence of both diseases.