COVID-19 infection is associated with an elevated risk for autoimmune blistering diseases while COVID-19 vaccination decreases the risk: A large-scale population-based cohort study of 112 million individuals

Background: Numerous diseases associated with COVID-19 infection and vaccination have been reported, including conditions such as the autoimmune blistering diseases (AIBDs) pemphigus and pemphigoid. However, robust evidence supporting these associations is lacking. Objective: To investigate the risk of developing AIBD following COVID-19 infection and vaccination. Methods: Population-based retrospective cohort study utilizing data from over 112 million patients. The risk of AIBD within 3 months was compared among 3 cohorts: COVID-19 infection, COVID-19 vaccination, and controls, along with 7 sensitivity analyses. Results: COVID-19 infection was associated with an increased risk of AIBD (hazard ratio [HR] 1.508, 95% CI 1.260-1.805), with the risk being more pronounced for pemphigus (HR 2.432, 1.618-3.657) compared to bullous pemphigoid (HR 1.376, 1.019-1.857). Conversely, COVID-19 vaccination was associated with an almost halved risk of AIBD (HR 0.514, 0.394-0.672), with the risk reduction most significant for pemphigus (HR 0.477, 0.241-0.946). Comparisons between COVID-19 infection and vaccination revealed a more than threefold increased risk of AIBD in the infection cohort (HR 3.130, 2.411-4.063), particularly for pemphigus (HR 5.508, 2.973-10.205). Limitations: Retrospective design and potential under-reporting of COVID-19 cases and vaccinations. Conclusion: COVID-19 infection significantly increases the risk of AIBD while vaccination appears to reduce this risk.