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To explore the humoral and T-cell response to the third COVID-19 vaccination in autoimmune hepatitis (AIH).Anti-SARS-CoV-2 antibody titers were prospectively determined in 81 AIH patients and 53 healthy age- and sex-matched controls7 days (median 35) after the first COVID-19 booster vaccination. The spike-specific T-cell response was assessed using an activation-induced marker assay (AIM) in a subset of patients.Median antibody levels were significantly lower in AIH compared to controls (10 908 vs. 25 000 AU/ml, p .001), especially in AIH patients treated with MMF (N = 14, 4542 AU/ml, p = .004) or steroids (N = 27, 7326 AU/ml, p = .020). Also, 48% of AIH patients had antibody titers below the 10% percentile of the healthy controls (9194 AU/ml, p .001). AIH patients had a high risk of failing to develop a spike-specific T-cell response (15/34 (44%) vs. 2/16 (12%), p = .05) and showed overall lower frequencies of spike-specific CD4 + T cells (median: 0.074% vs 0.283; p = .01) after the booster vaccination compared to healthy individuals. In 34/81 patients, antibody titers before and after booster vaccination were available. In this subgroup, all patients but especially those without detectable/low antibodies titers (100 AU/ml) after the second vaccination (N = 11/34) showed a strong, 148-fold increase.A third COVID-19 vaccination efficiently boosts antibody levels and T-cell responses in AIH patients and even seroconversion in patients with the absent immune response after two vaccinations, but to a lower level compared to controls. Therefore, we suggest routinely assessing antibody levels in AIH patients and offering additional booster vaccinations to those with suboptimal responses.