Two doses of Pfizer and BioNTech‘s vaccine are highly effective at protecting children 12 to 18 from a severe inflammatory condition associated with Covid infection, a new study found.

The Centers for Disease Control and Prevention, in a report published Friday, found that Pfizer’s vaccination was 91% effective at protecting adolescents against multisystem inflammatory syndrome, known as MIS-C.

The CDC study looked at 283 hospitalized patients ages 12 to 18 across 24 pediatric hospitals in 20 states from July through December 2021 when delta was the predominant variant. The analysis focused on the 12- to 18-year age group because Pfizer shots weren’t available to younger kids until November.

The CDC noted that vaccine efficacy against MIS-C caused by the omicron variant, which is now dominant in the U.S., could not be determined due to the timing of the study.

MIS-C is a serious condition in which different parts of the body become inflamed, such as the heart, lungs, kidneys, brain, skin, eyes, or gastrointestinal organs. Children usually develop MIS-C two to six weeks after an asymptomatic or mild Covid infection, according to the CDC.

More than 6,000 children have developed MIS-C since May 2020 and 55 have died, according to CDC data. The majority of MIS-C patients are Hispanic or Black, most are boys and half are between 5 and 13 years old. Of the known MIS-C cases, 98% tested positive for Covid while the other 2% had exposure to the virus, according to the CDC.

The CDC study compared 102 hospitalized MIS-C patients with 181 patients who either tested negative for Covid or did not have symptoms. The overwhelming majority of MIS-C patients, 95%, were unvaccinated. None of the five fully vaccinated MIS-C patients required life support, while 39% of unvaccinated MIS-C patients did need life support.

“This analysis lends supportive evidence that vaccination of children and adolescents is highly protective against MIS-C and COVID-19 and underscores the importance of vaccination of all eligible children,” the CDC concluded in its Morbidity and Mortality Weekly Report.

Children ages 5 and up are eligible to receive the two-dose Pfizer vaccine. Adolescents ages 12 and up are eligible for Pfizer booster shots at least five months after their second dose.