Atlanta—The hyperinflammatory condition associated with antecedent SARS-CoV-2 infection, multisystem inflammatory syndrome in children (MIS-C), caused great concern for parents when it was first reported in April 2020.

A new study in The Lancet Child & Adolescent Health looked at how cases were affected by vaccination against SARs-CoV-2 infection. In the U.S., reporting of MIS-C after vaccination is required under COVID-19 vaccine Emergency Use Authorizations (EAUs).

Researchers from the CDC sought to investigate cases of individuals aged 12 to 20 years with MIS-C after COVID-19 vaccination reported to passive surveillance systems or through clinician outreach to public health officials.

Potential cases of MIS-C after COVID-19 vaccination were investigated if they were reported to the CDC's MIS-C national surveillance system, the Vaccine Adverse Event Reporting System (coadministered by CDC and the FDA), and the CDC's Clinical Immunization Safety Assessment Project. Cases were adjudicated by a multidisciplinary team.

Using surveillance results from December 14, 2020, to August 31, 2021, the authors identified 21 young people with MIS-C after COVID-19 vaccination. Of those individuals, the median age was 16 years (range 12-20); 13 (62%) were male and eight (38%) were female. All 21 people were hospitalized; 12 (57%) were admitted to an ICU, and all were discharged home. Of those hospitalized, 15 (71%) had laboratory evidence of past or recent SARS-CoV-2 infection and six (29%) did not.

Researchers added that as of August 31, 2021, about 21 million youths aged 12 to 20 years had received one or more doses of a COVID-19 vaccine, making the overall reporting rate for MIS-C after vaccination 1.0 cases per million individuals receiving one or more doses in this age group, while the reporting rate in only those without evidence of SARS-CoV-2 infection was 0.3 cases per million vaccinated individuals.

"Here, we describe a small number of individuals with MIS-C who had received one or more doses of a COVID-19 vaccine before illness onset; the contribution of vaccination to these illnesses is unknown," the authors wrote. "Our findings suggest that MIS-C after COVID-19 vaccination is rare. Continued reporting of potential cases and surveillance for MIS-C illnesses after COVID-19 vaccination is warranted."

Background information in the article describes how MIS-C temporally associated with SARS-CoV-2 is a rare but serious complication of SARS-CoV-2 infection in children and adolescents; it generally occurs 2 to 6 weeks after SARS-CoV-2 infection and is characterized by fever, systemic inflammation, and multisystem organ involvement.

From May 14, 2020, to November 30, 2021, there were 5,973 cases were reported to the CDC's MIS-C national surveillance system.

When the Pfizer-BioNTech mRNA COVID-19 vaccine was granted EUA in December 2020 for those aged 16 years and older and then in May 2021 for youths aged 12 to 15 years, researchers sought to determine what effect that would have on MIS-C cases. "The pathogenesis of MIS-C is hypothesized to involve a dysregulated immune response to SARS-CoV-2 infection, and host genetics might alter susceptibility to developing MIS-C," the researchers explained.

They added, however, that surveillance for MIS-C after COVID-19 vaccination can be difficult because "MIS-C, in general, is a difficult diagnosis to make as it has no specific biomarkers and might resemble other disease processes, including acute COVID-19 infection, Kawasaki disease, and toxic shock syndrome."

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.