Case report of new‐onset ulcerative colitis after <scp>MVC‐COVI1901</scp> vaccine injection for <scp>SARS‐CoV</scp>‐2

<jats:title>Abstract</jats:title><jats:p>A 23‐year‐old man suffered from diarrhea after receiving the MVC‐COVI1901 vaccine. The patient then presented to our emergency department due to swelling and pain in his right knee. Synovial effusion studies of the right knee revealed inflammation. Gram and acid‐fast stains reported negative results and no crystals were found under a polarized light microscope. During his hospitalization, the patient underwent a colonoscopy and computed tomography (CT) due to bloody stool. Pancolitis was suspected under colonoscopy and an abdominal CT scan supported our diagnosis showing wall thickening and mucosal enhancement. Pathology showed distorted crypt architecture and acute cryptitis with abscesses. After excluding other causes of ulcerative colitis (UC), the patient was diagnosed with MVC‐COV1901 vaccine‐related UC and inflammatory bowel disease arthropathy. Subsequent presentation of UC and inflammatory bowel disease‐related arthropathy after receiving the MVC‐COVI1901 vaccine has not previously been reported. We speculate that the pathogenesis could be correlated to the vaccine's components (spike protein S‐2P adjuvanted with CpG 1018 and aluminum hydroxide) through the combination of 2 effects: the activation of Toll‐like receptor (TLR) 4 by S‐2P, and the activation of TLR9 and expression of interleukin‐13 by CpG‐1018 adjuvant. In conclusion, it is remarkable that the MVC‐COVI1901 vaccine may lead to the incidence of autoinflammatory diseases such as UC.</jats:p>