Altered liver function test after Covid-19 vaccines: A retrospective control group study

Background and purpose: Liver injury after Covid-19 vaccine has been described, although the incidence was not well established. We aimed to compare cumulative incidence of new onset liver test alteration after Covid-19 vaccination, and to compare with an historical control of influenza vaccination.

Methods: We conducted a retrospective cohort study which included adults who received at least one dose of Covid-19 vaccine from January 1 to May 30, 2021 and a control group who received a single dose of influenza vaccine during 2019, in a tertiary medical center from Argentina.

Results: We included 29 798 patients in Covid-19 vaccine group and 24 605 in influenza vaccine group. Liver function tests were performed in 7833 (26.9%) in Covid-19 vaccine group and 8459 (34.37%) in influenza vaccine group. Cumulative incidence at 90 days of new onset liver enzyme test alteration was 4.7 per 1000 (95% 4.0-5.5) for Covid-19 group, and 5.1 per 1000 (95% 4.3-6.1) for the influenza vaccine group (p value = 0.489). Two patients in the Covid-19 vaccine group developed immune mediated liver injury.

Conclusions: We found no difference in liver test alteration between groups. These findings support the safety of Covid-19 vaccines. While we have identified two cases that are consistent with immune mediated liver injury following COVID-19 vaccination, we believe that the available data is insufficient to attribute them solely to the vaccination.