[Autoimmune hepatitis developed after COVID-19 vaccination and ameliorated temporarily but relapsed or stopped improving, and finally resolved by steroid therapy:a report of three cases].

The severe acute respiratory syndrome coronavirus 2 vaccine has contributed to infection control and the prevention of complications due to coronavirus disease 2019 (COVID-19). Conversely, the COVID-19 vaccine has been associated with adverse effects due to liver injury caused by autoimmunity or drugs. To date, Japanese journals have only published five reports of autoimmune liver damage associated with the COVID-19 vaccination. Although the pathogenic mechanism has not yet been fully elucidated, corticosteroids or azathioprine have shown effectiveness in certain patients. However, there have been cases of liver injury resulting in deaths. Here, we encountered three patients who developed autoimmune hepatitis (AIH) within 10 days following vaccination. All three patients were treated with prednisolone (PSL) and achieved remission. However, the serum alanine aminotransferase levels in all cases were observed to either increase or cease to improve during the therapeutic course before PSL administration. It is therefore imperative to closely monitor liver injury after the COVID-19 vaccination. In cases where AIH is suspected and a recurrence of liver dysfunction occurs, PSL may be administered. Future considerations should not only encompass the underlying mechanism by which autoimmunity contributes to the development of liver injury following COVID-19 vaccination but also the optimal treatment period for PSL and the long-term prognosis of AIH after COVID-19 vaccination.