Ulrikka Nygaard (Copenhagen University Hospital) and co-investigators also “found vaccine effectiveness to be high against MIS-C,” which they suggest “was due to protection from infection and, possibly, a decreased incidence of MIS-C after breakthrough infection.”

Autoantibodies against IL-1Ra are present in a large proportion of patients with MIS-C, say researchers.

They conclude: “Until published data that define best practices are available, these data provide clinicians with additional evidence to guide treatment for MIS-C.”

Campbell and co-authors conclude: “The estimates and approach in this study provide baseline data prior to implementation of interventions, such as SARS-CoV-2 vaccination for children, allowing for subsequent monitoring of MIS-C as an outcome, as prevention of SARS-CoV-2 infection would be expected to reduce incidence of MIS-C.”

They found that median CXCL9 levels were significantly higher among 11 children with MIS-C compared with nine with Kawasaki disease, at 1730 versus 278 pg/mL, while the CXCL9 elevations in the MIS-C group were “comparable” to those seen in nine patients with systemic JIA-associated MAS.

The guidance advises on the diagnosis of MIS-C, discusses the similarities and differences relative to Kawasaki disease, and provides recommendations on cardiac management, immunomodulatory treatment, and antiplatelet and anticoagulation therapy.