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Cosmos Study

98% of MIS-C Hospitalizations Were Unvaccinated Pediatric Patients

Abstract: Pediatric COVID and MIS-C hospitalizations remain low, especially for those who are vaccinated.
January 28, 2022
Sam Butler, MD | Xander Posner, MPH

While pediatric hospitalization rates for COVID-19 remain much lower than adult hospitalization rates for the same conditions, less is known about the differences in hospitalization rates for COVID-vaccinated and unvaccinated pediatric patients. Additionally, we sought to understand whether COVID vaccination was associated with hospitalizations for multi-system inflammatory syndrome in children (MIS-C), a serious condition associated with COVID-19.

When comparing pediatric COVID cases and MIS-C cases over time, we found that MIS-C cases tend to peak after COVID cases peak, as shown in Figure 1.

Figure 1
Weekly Pediatric COVID-19 and MIS-C Cases
Weekly Pediatric COVID-19 and MIS-C Cases
Figure 1. Weekly rates of COVID-19 and MIS-C infections in pediatric populations.

We evaluated COVID hospitalizations for 5- to 20-year-olds and MIS-C hospitalizations for 0- to 20-year-olds in 2021 after the vaccine became available for pediatric patients. Overall, COVID hospitalization rates for pediatric patients remained low, with just 2% of admissions being for COVID. Of the 699 pediatric hospitalizations for COVID, 513 (73%) were for unvaccinated patients. Of the 1,499 pediatric hospitalizations for MIS-C, 1,474 (98%) were for unvaccinated patients.

Figure 2
Pediatric COVID-19 and MIS-C Hospitalizations by Vaccination Status
Pediatric COVID-19 and MIS-C Hospitalizations by Vaccination Status
Figure 2: COVID-19 and MIS-C hospitalizations for pediatric patients by vaccination status. The gray area represents the proportion of hospitalized patients who were vaccinated, while the maroon area represents the proportion of hospitalized patients who were unvaccinated.

These data suggest that in addition to the known decrease in likelihood to be hospitalized for COVID when vaccinated1, COVID vaccination might also play a role in decreasing the likelihood of developing MIS-C.

These data come from Cosmos, a HIPAA-defined Limited Data Set of more than 126 million patients from 156 Epic organizations including 889 hospitals and 19,420 clinics, serving patients in all 50 states.

  1. The Centers for Disease Control and Prevention. COVID-19 Vaccines Work. https://www.cdc.gov/coronavirus/2019-ncov/vaccines/effectiveness/work.html. Accessed on January 10, 2021.