Cases of Rapid Hepatitis B Surface Antigen Reduction after COVID-19 Vaccination.

Objective One of the therapeutic goals for chronic infection with hepatitis B virus is the clearance of hepatitis B surface antigen (HBsAg) from the blood, as a high load of HBsAg has been proposed to induce antigen-specific immunotolerance. To achieve HBsAg reduction, Pegylated interferon and nucleos (t) ide analogs are used to treat chronic hepatitis B. Following the coronavirus disease 2019 (COVID-19) outbreak, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has rapidly spread worldwide, and vaccination with mRNA COVID-19 vaccines has been conducted since 2021 in Japan. We experienced three clinical cases in which HBsAg levels rapidly decreased after injection of the COVID-19 vaccine without any incentive. Method To examine whether the vaccine administration was involved in the HBsAg reduction, the number of patients with chronic hepatitis B showing a change in the HBsAg levels during the period before the commencement of the COVID-19 vaccination program in Japan (i.e. until the end of 2020; pre-vaccination-program period) was compared to the number of those who showed a change in HBsAg levels after the initiation of the program (i.e. 2021 onwards; post-vaccination-program period). Results The number of patients whose HBsAg levels was reduced by >50% per year was prominent after the initiation of the vaccination program. Although the involvement of vaccination in HBsAg reduction was not statistically proven (p=0.0532), the result suggests that the administration of COVID-19 vaccines may have been involved in HBsAg reduction in patients with chronic hepatitis B. Conclusion COVID-19 vaccines may be involved in HBsAg reduction.