Severity of Pediatric Inflammatory Multisystem Syndrome Temporally Associated with SARS-CoV-2 Diminished During Successive Waves of the COVID-19 Pandemic: Data from a Nationwide German Survey.

Objective: To elucidate how the clinical presentation of Pediatric Inflammatory Multisystem Syndrome temporally associated with Severe Acute Respiratory Syndrome-related Coronavirus 2 (PIMS-TS) was influenced by the successive variants of concern (VOC) and patient age.

Study design: A nationwide PIMS-TS registry was established in Germany in May 2020, shortly after the first cases were described in the US and United Kingdom. The registry captured information on patient characteristics, clinical course, laboratory findings, imaging, and outcome. All pediatric hospitals in Germany, along with one in Austria, were invited to participate. Between March 18, 2020, and April 30, 2023, 920 cases were reported.

Results: By examining a combination of data on clinical features, laboratory findings, treatment, imaging results, and outcomes, our analysis demonstrated disease severity to have continuously declined over the course of the Wildtype, Alpha, Delta, and Omicron waves. Based on clinical symptoms, laboratory and diagnostic findings, and intensive care unit admission rates, older children, irrespective of the related VOC, were shown to experience more severe, acute PIMS-TS; however, they had lower rates of coronary aneurysm.

Conclusions: During the course of COVID-19 pandemic, as each new VOC emerged, PIMS-TS lessened in severity. In parallel, older children came to experience more debilitating disease.