Multisystem Inflammatory Syndrome Due to COVID-19 Infection in Vaccinated Versus Unvaccinated Adolescents: A Case Report

Symptoms of COVID-19 infection are usually mild in the healthy pediatric population. In some pediatric patients, COVID-19 infection can lead to multisystem inflammatory syndrome in children (MIS-C). We report two cases. Case 1 is a rare case of MIS-C symptoms, presenting with myalgia, chest pain, and fever three days after the second dose of the Pfizer-BioNTech COVID-19 vaccine, which is compared with Case 2, which is a case of MIS-C in an unvaccinated patient with COVID-19 infection who was noted to have acute kidney injury and fluid refractory hypotension. Although MIS-C was reported as a vaccine side effect, we conclude that COVID-19 infection led to the development of MIS-C in our case, not the COVID-19 vaccine. MIS-C symptoms were also noted to be less severe after the COVID-19 vaccine than in the unvaccinated patients.