The COVID-19 vaccine protects against disease and severe effects, but can it help reduce the risk of multisystem inflammatory syndrome in children (MIS-C)?
The immunogenicity and effectiveness of COVID-19 mRNA vaccines in teenagers are well known. Whether these vaccines might have an impact on multisystem inflammatory syndrome in children (MIS-C) was an unknown variable. Following the start of the Delta wave, French health authorities recommended vaccination in all children aged 12 years and older. A report examined the risk of MIS-C among these children during the next couple of months.1
The investigators included any patient who was diagnosed with MIS-C and was admitted to 1 of 41 pediatric intensive care units in France between September 1, 2021, and October 31, 2021. Patients who had been reported to the French Public Health Agency, but did not require hospitalization in the same period were. Data were recorded for age, sex, admission to a pediatric intensive care unit, and vaccination status.
At the beginning of the French COVID-19 vaccination campaign in June 2021, 2,2% of the 4,989,013 teenagers had received at least 1 dose of a COVID-19 vaccine and 0.2% were considered fully vaccinated. By October 31, 2021, 76.7% of teenagers had been administered at least 1 dose and the 72.8% were fully vaccinated. The vast majority of vaccines used were the Pfizer/BioNTech vaccine, with Moderna and other vaccines making up less than 5% of the doses administered. During the study period, 107 children were hospitalized for MIS-C, of which 33 were teenagers who were eligible for vaccination. The adolescents with MIS-C had a median age of 13.7, were mostly male, and 29 were admitted to the pediatric intensive care unit. None of them were fully vaccinated and 26 had not been vaccinated at all. Seven of the patients had been given 1 dose, with a median interval between administration and onset of MIS-C of 25 days. The hazard ratio for MIS-C was 0.09 (95% CI, 0.04-0.21; P < .001) following a first vaccine dose when compared with teenagers who were unvaccinated.
The investigators concluded that vaccination appears to have a positive impact on the incidence of MIS-C in teenagers. The timing of the median interval between receiving a first dose and onset of MIS-C indicates that the COVID-19 infection likely occurred before a strong immune response had occurred. The lack of MIS-C cases among the fully vaccinated teenagers indicates that 2 doses may provide efficient protection. Research should be done in children aged 5 to 11 years, now that vaccines have been authorized for the age group.