The Lancet Child and adolescent health: Multi-s
Peer review / Observational study / People
- Researchers report surveillance data recording cases of multisystem inflammatory syndrome in children (MIS-C) among people aged 12 to 20 who had received at least one dose of a COVID-19 vaccine in the first nine month of the US COVID-19 vaccination program.
- During the nine-month period, more than 21 million children and adolescents in this age group received at least one dose of the COVID-19 vaccine, and a total of 21 cases of MIS-C were identified, suggesting that MIS-C has occurred in one in one million vaccinees. , which is significantly lower than previous estimates of 200 cases per million among unvaccinated people infected with SARS-CoV-2.
- Six identified cases of MIS-C had no evidence of SARS-CoV-2 infection, suggesting that the rate of cases without evidence of SARS-CoV-2 infection was 0.3 cases per million people vaccinated in this age group. The authors emphasize that they are unable to determine if the vaccine contributed to these rare cases, or if there were other reasons for the illness, such as other unrecognized underlying inflammatory conditions.
Reported cases of multisystem inflammatory syndrome (MIS-C) in children and adolescents who received at least one dose of COVID-19 vaccine were rare (estimated at one case per million vaccinated individuals in this age group). According to an observational study published in The Lancet Child and adolescent health newspaper.
Although there is no direct comparator available, this survey found that the rate of MIS-C cases among vaccinated children and adolescents ages 12 to 20 in the United States is significantly lower than previously published estimates. in unvaccinated people aged 12 to 20 who had been infected with SARS. -CoV-2 from April to June 2020. 
Dr. Anna R. Yousaf of the United States Centers for Disease Control and Prevention (CDC) says: “As part of the overall effort to monitor COVID-19 vaccine safety in the United States, the CDC closely monitors cases of MIS-C in vaccinated children. . Our results suggest that cases of MIS-C after COVID-19 vaccination are rare and that the likelihood of developing MIS-C is much higher in unvaccinated children who contract COVID-19. Vaccination against COVID-19 is recommended for anyone age 5 and older in the United States for the prevention of COVID-19. » 
MIS-C, also known as pediatric inflammatory multisystem syndrome (PIM-TS), is a rare disease associated with SARS-CoV-2 infection that was first recognized in April 2020. thinks MIS-C is an immune overreaction that occurs about two to six weeks after SARS-CoV-2 infection in children and adolescents. Symptoms include fever, rash, eye redness, and gastrointestinal symptoms (eg, diarrhea, upset stomach, nausea) and may lead to multiple organ failure. In the United States, reporting of possible cases of MIS-C after vaccination is required as part of emergency use authorizations for the COVID-19 vaccine.
This study investigated cases of MIS-C in children and adolescents aged 12-20 years reported during the first nine months of COVID-19 vaccination rollout in the United States (December 14, 2020 to August 31, 2021).  A team of medical specialists and epidemiologists reviewed 47 reports of potential MIS-C illness occurring in a person between the ages of 12 and 20 at any time after a dose of the COVID-19 vaccine. Of these 47 reports, 21 met the CDC MIS-C criteria. These were separated into those with and without evidence of past or recent SARS-CoV-2 infection from laboratory testing. They calculated case notification rates using CDC national vaccine surveillance data on the number of individuals ages 12 to 20 in the United States who received one or more doses of the COVID-19 vaccine. .
Of the 21 MIS-C cases, 15 had evidence of past or recent SARS-CoV-2 infection, while six did not. More than 21 million children and adolescents aged 12 to 20 had received one or more doses of a COVID-19 vaccine, representing one reported case per million people vaccinated in this age group. The MIS-C notification rate for people without evidence of SARS-CoV-2 infection was 0.3 cases per million people vaccinated.
The authors emphasize that they are unable to determine whether vaccination contributed to MIS-C disease in these rare cases. As MIS-C was first identified during the pandemic, there is no baseline rate of inflammatory disease in children and adolescents of unidentified cause to estimate a baseline number of cases expected over a period of nine months, regardless of COVID-19 infection or vaccination. It is possible that some of the identified cases had other unrecognized inflammatory conditions that coincidentally occurred after vaccination.
Of the 15 people previously infected with SARS-CoV-2, three were diagnosed with MIS-C outside of the typical two to six week (14─42 day) period in which MIS-C illness Later C is most likely to occur. These three people had the start of MIS-C 105 days, 191 days and 238 days after their positive SARS-CoV-2 test.
All 21 people were hospitalized, 12 were admitted to an intensive care unit and all were sent home. The median age was 16; 13 were male and eight were female.
All people with MIS-C in the study received the Pfizer-BioNTech COVID-19 vaccine (BNT162b2), which was the only COVID-19 vaccine licensed in the United States for use in those under 18 years of age during the study period. 11 people received one dose and 10 received two doses of the vaccine before MIS-C disease onset. The median time from dose to hospitalization was eight days for those who received one dose of vaccine and five days for those who received two.
Dr. Yousaf continues, “As with COVID-19 disease, clinicians and researchers are still learning about MIS-C. Our survey highlights the challenges of diagnosing MIS-C, the importance of considering alternative diagnoses, and the need to monitor MIS-C disease. 
The authors note some additional limitations to their study. It is possible that some of the identified cases of MIS-C had other inflammatory diseases with similar symptoms, as there is no definitive test to diagnose MIS-C. Because laboratory tests for COVID-19, including antibody tests, are imperfect, some cases may have been misclassified. Children often have mild or asymptomatic infection, and milder infections may be less likely to generate antibodies, which can lead to previous undetected infections. It is also possible that not all cases of MIS-C post-vaccination were reported to the surveillance system, which could lead to under-reporting of the number of cases.
Writing in a linked comment, lead author Dr Mary Beth Son of Boston Children’s Hospital, USA (who was not involved in the study), says: “Their findings are overall quite reassuring. Cases of MIS-C after COVID-19 vaccination have been reported in only 1 in a million people aged 12 to 20 who received one or more doses of a COVID-19 vaccine, and 15 (71%) of 21 people with MIS-C had a laboratory test. evidence of prior SARS-CoV-2 infection, casting doubt on attribution. This timely report is of particular interest to healthcare providers, scientists and policymakers, given the continued and widespread transmission of the omicron variant (B.1.1.529). …As the pandemic continues to challenge our global community and the scrutiny of COVID-19 vaccines persists, the report by Yousaf and colleagues is a welcome addition to the growing literature supporting the safety and effectiveness of vaccination against SARS CoV-2.
NOTES TO EDITORS
This study was funded by the US Centers for Disease Control and Prevention (CDC). It was conducted by researchers from the CDC COVID-19 Response Team.
The labels were added to this news release as part of a project led by the Academy of Medical Sciences to improve evidence reporting. For more information, please see: http://www.sciencemediacentre.org/wp-content/uploads/2018/01/AMS-press-release-labelling-system-GUIDANCE.pdf if you have any questions or comments , please contact The Lancet Press Office [email protected]
 Using a denominator of SARS-CoV-2 infections in unvaccinated people, a previous study from April to June 1, 2020 estimated an MIS-C rate of 224 per million SARS-CoV infections -2 in children aged 11-15 and 164 per million in 16-20 year olds: https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2780861
 Direct quote from the author and not found in the text of the article.
 The researchers identified possible cases from the CDC’s national MIS-C surveillance system, the Vaccine Adverse Event Reporting System (co-administered by the CDC and the U.S. Food and Drug Administration), and the Project CDC Clinical Immunization Safety Assessment.
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The Lancet Child and adolescent health
The title of the article
Reported cases of multisystem inflammatory syndrome in children aged 12 to 20 in the United States who received a COVID-19 vaccine, December 2020 to August 2021: a surveillance survey
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Conflict of Interest Statement
The MOE reports a grant from the Pediatric Heart Network of the United States National Institutes of Health (NIH). SK reports grants from NIH and Pfizer. EPS brings in grants from Pfizer, consulting fees from Sanofi Pasteur, and serves on the Data Safety Monitoring Board for vaccine trials sponsored by the NIH’s Division of Microbiology and Infectious Diseases. MAS reports payment from NIH. KME reports consulting fees from IBM and BioNet and participation on the data security oversight committee or advisory board from Roche, Pfizer, Sanofi, Moderna, X-4 Pharma, Merck and Seqirus. CBC reports grants from NIH and Merck Vaccines; UpToDate royalties; consulting fees from GlaxoSmithKline, Horizon Pharma, Altimmune, Premier Healthcare and Vindico; payment for forensic testimony from multiple firms (none related to this investigation); a US patent for staphylococcal antibody (number 10,981,979); participation in a data security oversight committee or advisory committee for Astellas; and is president of the Pediatric Infectious Diseases Society. MBS reports a fiduciary role as a partner in Southern California Permanente Medical Group. The BLS and CPB report an epidemiology and laboratory capacity grant from the CDC. JHS reports unpaid co-direction of the Society for Cardiovascular Magnetic Resonance pediatric multicenter research. All other authors declare no competing interests.