Rare Multisystem Inflammatory Syndrome Detected in Vaccinated Young

Some vaccinated youngsters in the 12–20 age group have reported a hyper-inflammatory condition where the body’s immune system goes into overdrive and shows symptoms of fever and systemic inflammation involving multiple organ systems, according to a study published Tuesday.

There were 5,973 cases of Multisystem Inflammatory Syndrome in Children (MIS-C) reported to the MIS-C national surveillance system of the U.S. Centers for Disease Control and Prevention (CDC) between May 14, 2020, and Nov. 30, 2021. MIS-C usually manifests two to six weeks after inoculation and is characterized by severe illness that requires hospitalization. The authors of the peer-reviewed Lancet study looked into data between Dec. 14, 2020, and Aug. 31, 2021. Over 21 million 12 to 20-year-old individuals received at least one dose of a COVID-19 vaccine as of Aug. 31, 2021.

The researchers found 21 young people with a mean age of 16 years from the demographic who showed symptoms consistent with MIS-C. Of these, 13 were male and eight were female. Out of the 21 individuals, 11 developed MIS-C after receiving the first dose of the vaccine, with the remaining 10 developing the illness after taking the second dose.

“All 21 were hospitalized: 12 (57 percent) were admitted to an intensive care unit and all were discharged home. 15 (71 percent) of 21 individuals had laboratory evidence of past or recent SARS-CoV-2 infection, and six (29 percent) did not,” the report said.

The overall reporting rate of MIS-C among this age group of over 21 million vaccinated individuals was one per million. The reporting rate among those without evidence of COVID-19 infection was only 0.3 per million vaccinated individuals.

These rates are lower than a previous study on the issue that had proposed an MIS-C reporting rate of 224 per million among individuals aged 11 to 15 and a rate of 164 per million among those aged between 16 and 20.

“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 authors wrote.

Another study found that 98 percent of MIS-C hospitalizations were among unvaccinated pediatric patients. According to the researchers, MIS-C cases tend to peak after the peak in COVID cases.

Out of the 699 pediatric hospitalizations for COVID-19, 513 cases or 73 percent were found among unvaccinated individuals, claimed the study published at Epic Research on Jan. 28. “Of the 1,499 pediatric hospitalizations for MIS-C, 1,474 (98 percent) were for unvaccinated patients,” from the research report.

In its Jan. 14 Morbidity and Mortality Weekly Report (MMWR), the CDC proposes that two doses of Pfizer vaccine had an estimated effectiveness rate of 91 percent against MIS-C, thus suggesting its use among individuals between the ages of 12 and 18. However, MMWR is not a medical journal or peer-reviewed, but only CDC policy advocacy.

The National Institutes of Health (NIH) has proposed multiple treatment options for pediatric patients with MIS-C. This includes initial immunomodulatory therapy, intensification immunomodulatory therapy, antithrombotic treatment, antiviral therapy, and critical care management.