Abstract
Background: BNT162b2 is a widely used mRNA COVID-19 vaccine for which 8.2% of participants above the age of 56 years have reported diarrhea as an adverse event. This case report highlights the possibility of eosinophilic colitis in post-vaccination diarrhea.
Case report: A 72-year-old male patient presented with generalized colicky abdominal pain and acute diarrhea after receiving the first dose of the BNT162b2 vaccine. Laboratory examination revealed peripheral blood eosinophilia with cecal and ascending colon mucosal eosinophilia with 100–130 cells/HPF and eosinophilic cryptitis. The patient’s symptoms and eosinophilia resolved spontaneously and did not recur after the second dose of vaccination. More research is needed to confirm eosinophilic colitis as a possible vaccine adverse reaction.