Multisystem Inflammatory Syndrome in Children and SARS-CoV-2 Variants: A Two-Year Ambispective Multicentric Cohort Study in Catalonia, Spain

Abstract

Background : Multisystem inflammatory syndrome in children (MIS-C) is a rare but severe disease temporarily related to SARS-CoV-2. We aimed to describe the epidemiological, clinical and laboratory findings of all the MIS-C cases diagnosed in children <18 years old in Catalonia (Spain) to study their trend throughout the pandemic.

Methods: Multicenter ambispective observational cohort study (April 2020-April 2022). Data were obtained from the COVID-19 Catalan surveillance system and from all the hospitals in Catalonia. We analyzed MIS-C cases regarding SARS-CoV-2 variants for demographics, clinical symptoms, severity, monthly MIS-C incidence, ratio between MIS-C and accumulated COVID-19 cases, and associated rate ratios (RR).

Findings: Among 555,848 SARS-CoV-2 infections, 152 children were diagnosed with MIS-C. Monthly MIS-C incidence was 4·1 (95% CI: 3·4-4·8) per 1,000,000 people, and 273 (95% CI: 230-316) per 1,000,000 SARS-CoV-2 diagnosis (i.e., one case per 3,700 SARS-CoV-2 infections). During the Omicron period, MIS-C RR was 8·2 (95% CI: 5·7-11·7) per 1,000,000 SARS-CoV-2 infections, significantly lower (p<0.001) than for previous variant periods, in all age groups. Median age of MIS-C was 8 [4-11] years, 62·5% male, and 80·2% without comorbidities. Common symptoms were gastrointestinal findings (88·2%) and fever >39ºC (81·6%), nearly 40% had an abnormal echocardiography and 7% coronary aneurysm. Clinical manifestations and laboratory data were not different throughout the variant periods (p>0·05).

Interpretation: The rate ratio between MIS-C cases and SARS-CoV-2 infections was significantly lower in the Omicron period for all the age groups, including those not vaccinated, suggesting that the variant could be the main factor for this shift in the MIS-C trend. Regardless of variant type, the patients had similar phenotypes and severity throughout the pandemic.

Note:
Funding Information: This study has received funding for the data analysis from the “Fundació la Marató TV3” with file number 202134-30-31.

Conflict of Interests: The authors declare that they have no conflicts of interest.

Ethical Approval: The study was reviewed and approved by the research ethics committee of the coordinating center (file number PR(AMI)271/2021). All the participating sites obtained their approval from the respective ethics committees for the collection of data related to the MIS-C cases. This research was based on the agreement established in Regulation 2016/679 of the European Parliament and the Council of Europe of April 27, 2016 on Data Protection, and Organic Law 3/2018 of December 5 on the Protection of Personal Data and the Guarantee of Digital Rights.

Keywords: MIS-C, SARS-CoV-2, COVID-19, epidemiology, child