Abstract
Septic arthritis is a serious medical emergency associated with high morbidity and mortality. A 49-year-old man with diabetes undergoing hemodialysis developed right shoulder pain and fever following his sixth dose of the COVID-19 vaccine. Twelve days after vaccination, his fever persisted, and computed tomography imaging revealed a fluid collection around the right shoulder joint. Culture of the synovial fluid detected methicillin-susceptible Staphylococcus aureus, leading to a diagnosis. Intravenous administration of ceftriaxone was effective and de-escalated to cefazolin and then oral cefaclor. The patient was discharged without complications. Caution is warranted because unexpected complications may arise after vaccination in individuals with multiple comorbidities.