Background: From May 2020 to January 2021, we enrolled 1233 health care workers (HCW) from Danish Hospitals in a randomized trial evaluating whether Bacille Calmette-Guérin (BCG) provides protection against COVID-19. Participants were randomized 1:1 to BCG vs saline and followed for 6 months. From December 2020, Covid-19 vaccines were offered to the HCW. In most cases, BCG vaccination results in a characteristic scar. Reactivation of the BCG scar has been described in children during viral infections and following influenza vaccination, but is mostly associated to Kawasaki's disease, a disease entity with pathogenesis likely similar to the child Covid-19 complication MIS-C: Multi-System Inflammatory Syndrome. Reactivation of scars after neonatal BCG vaccination has recently been described in four women after Covid-19 mRNA vaccination. Two of our trial participants experienced reactivation of their novel BCG scars after receiving mRNA Covid-19 vaccination 6 to 8 months post-BCG.