Two cases of systemic lupus erythematosus after administration of severe acute respiratory syndrome coronavirus 2 vaccine.

Although there is a great demand for increased coronavirus disease 2019vaccination worldwide, rare side effects of the vaccines in susceptible individuals are attracting attention. We recently treated two patients who developed systemic lupus erythematosus after administration of a severe acute respiratory syndrome coronavirus 2 vaccine from Pfizer-BioNTech or Moderna. While causal relationships between vaccination and adverse events are difficult to discern due to both confounding and masking factors, our findings suggest that attention to possible adjuvant-related autoimmune diseases in certain individuals receiving severe acute respiratory syndrome coronavirus 2 vaccines is appropriate.