The spread of COVID-19 infection has led to rapid vaccine development. It has been shown that vaccination may lead to complications like adult-onset Still's disease. We report a case of a 47-year-old Latvian male who presented with a sore throat, persistent leukocytosis, a high spiking fever, and weakness within two days after receiving the first dose of the Moderna COVID-19 vaccine in April 2021. The patient was initially treated with empirical antibiotics; however, the symptoms did not improve...