117 cases of multisystem inflammation syndrome in children identified during 2023

In 2023, 117 cases of multisystem inflammation syndrome in children (MIS-C) were reported, with 26 percent of patients having onset during August to October, according to research published in the March 14 issue of the U.S. Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report.

Anna R. Yousaf, M.D., from the CDC in Atlanta, and colleagues describe 2023 MIS-C cases and compare them to cases reported earlier in the COVID-19 pandemic.

The researchers found that 117 MIS-C patients had illness onset in 2023, and of these patients, 31 (26 percent) had onset during August to October, following increased COVID-19 activity earlier in the summer. This finding represented an increase of two-thirds in case counts compared with the 19 cases (16 percent) reported during the previous three-month period.

In 2023, the overall incidence of MIS-C was 0.11 cases per million person-months, representing an 80 percent decrease compared with April to December 2022 (0.56 cases per million person-months).

Overall, 58 percent of the MIS-C patients with illness onset in 2023 had no underlying medical conditions. Ninety-six percent of the patients were age-eligible for COVID-19 vaccination, but only 18 percent had received any COVID-19 vaccine.

"Clinicians should recognize that MIS-C might occur, especially during and after periods of increased COVID-19 activity, and should be familiar with treatment guidelines," the authors write.