MIS-C across three SARS-CoV-2 variants: Changes in COVID-19 testing and clinical characteristics in a cohort of US children

As new variants of SARS-Co-V 2 have emerged over time and Omicron sub-variants have become dominant, the severity of illness from COVID-19 has declined despite greater transmissibility. There are fewer data on how the history, diagnosis, and clinical characteristics of multisystem inflammatory syndrome in children (MIS-C) have changed with evolution in SARS-CoV-2 variants. We conducted a retrospective cohort study of patients hospitalized with MIS-C between April 2020 and July 2022 in a tertiary referral center. Patients were sorted into Alpha, Delta, and Omicron variant cohorts by date of admission and using national and regional data on variant prevalence. Among 108 patients with MIS-C, significantly more patients had a documented history of COVID-19 in the two months before MIS-C during Omicron (74%) than during Alpha (42%) (p = 0.03). Platelet count and absolute lymphocyte count were lowest during Omicron, without significant differences in other laboratory tests. However, markers of clinical severity, including percentage with ICU admission, length of ICU stay, use of inotropes, or left ventricular dysfunction, did not differ across variants. This study is limited by its small, single-center case series design and by classification of patients into era of variant by admission date rather than genomic testing of SARS- CoV-2 samples.Conclusion: Antecedent COVID-19 was more often documented in the Omicron than Alpha or Delta eras, but clinical severity of MIS-C was similar across variant eras.

Automated summary

With the emergence of new variants of SARS-CoV-2, particularly the Omicron sub-variants, the severity of illness from COVID-19 has decreased despite higher transmissibility. However, there is limited data on how the history, diagnosis, and clinical characteristics of multisystem inflammatory syndrome in children (MIS-C) have changed with the evolution of SARS-CoV-2 variants. A retrospective cohort study was conducted on hospitalized MIS-C patients between April 2020 and July 2022, categorizing patients into Alpha, Delta, and Omicron variant cohorts based on admission dates and variant prevalence data. The study found that more MIS-C patients had a documented history of COVID-19 in the two months before MIS-C during the Omicron era compared to the Alpha era, but there were no significant differences in clinical severity across different variant eras.