SARS-CoV-2 variants are associated with different clinical courses in children with MIS-C.

Background: Recent infection with SARS‑CoV‑2 in children has been associated with multisystem inflammatory syndrome in children (MIS-C). SARS‑CoV‑2 has undergone different mutations. Few publications exist about specific variants and their correlation with the severity of MIS-C.

Methods: This was a single-center, retrospective study including all patients admitted with MIS-C at Rady Children's Hospital-San Diego between May 2020 and March 2022. Local epidemiologic data, including viral genomic information, were obtained from public records. Demographics, clinical presentation, laboratory values, and outcomes were obtained from electronic medical records.

Results: The analysis included 104 pediatric patients. Four MIS-C waves were identified. Circulating variants in San Diego during the first wave included clades 20A to C. During the second wave, there were variants from clades 20A to C, 20G, 21C (Epsilon), 20I (Alpha), and 20J (Gamma). The third wave had Delta strains (clades 21A, 21I, and 21J), and the fourth had Omicron variants (clades 21K, 21L, and 22C). MIS-C presented with similar symptoms and laboratory findings across all waves. More patients were admitted to the pediatric intensive care unit (PICU) (74%) and required inotropic support (63%) during the second wave. None of the patients required mechanical circulatory support, and only two required invasive ventilatory support. There was no mortality.

Conclusions: The various strains of SARS-CoV-2 triggered MIS-C with differing severities, with the second wave having a more severe clinical course. Whether the differences in disease severity across variants were due to changes in the virus or other factors remains unknown.