Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which caused the coronavirus disease 2019 (COVID-19), started worldwide in December 2020. Multisystem inflammatory syndrome in children and adults (MIS-C/A) is a post-SARS-CoV-2 infection syndrome with an estimated incidence of 1 in 3000 to 4000 (ages <21 years). In this report, we have tried to explain 2 pediatric cases of multisystem inflammatory syndrome in children and adults (MIS-C/A) post severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination (MIS-V). 

Five weeks after his first (and only) Pfizer-BioNTech SARS-CoV-2 vaccine (left deltoid), a healthy 12-year-old boy was brought to the emergency department with 3 days of low-grade fever and painful left axillary lymphadenopathy and redness. An ultrasound confirmed nonsuppurative adenitis. He was prescribed cephalexin for cellulitis. He returned 2 days later with a fever (39.4°C) an extension of an erythematous rash to the anterolateral left thorax, and a new pruritic macular rash behind both knees and thighs. 

He was admitted to the hospital, but he developed a generalized rash, cracked lips, and strawberry tongue within 24 hours. Investigations revealed marked lymphopenia, elevated C-reactive protein (CRP), and very elevated troponins. Additionally, he was diagnosed with MIS-C. Other diagnoses included Kawasaki disease (KD), toxic shock syndrome, Mycoplasma pneumoniae induced rash and mucositis or Stevens-Johnson Syndrome, post viral (non-SARS-CoV-2) peri-myocarditis, adenoviral infection, and MIS-V.

As a result, all antibiotic therapy was changed to azithromycin and was discontinued after a diagnosis of Mycoplasma pneumoniae-induced rash and mucositis and Stevens-Johnson Syndrome was excluded. Troponins normalized and he remained well at 6 weeks post discharge, at which time ASA was stopped.

As a result, it can be concluded that surveillance for rare adverse events following immunization should continue, especially now that SARS-CoV-2 vaccination is approved in the 5-to-11-year age group that has had the highest risk of developing MIS-C post-SARS-CoV-2 infection. 

Source: Pediatrics. 2022 Aug 1;150(2): e2021055956. doi: 10.1542/peds.2021-055956.