June 10 (UPI) -- Black and Hispanic children in the United States are nearly 10 times as likely to develop severe inflammation in multiple bodily organs due to COVID-19 than White children, a study published Thursday by JAMA Network Open found.
Young people of Asian and Pacific Island descent nationally had a three-fold higher risk for developing this complication, called multi-system inflammatory syndrome in children, or MIS-C, compared with White youths, the data showed.
However, MIS-C remains extremely rare, with just 316 cases per 1 million children infected with the coronavirus, the researchers, part of the Centers for Disease Control and Prevention's COVID-19 Response Team, said.
Children under age 10 appear to be at the highest risk, with the condition occurring most often in those between ages 6 and 10, according to the researchers.
"Multi-system inflammatory syndrome in children is a rare but serious complication associated with COVID-19," study co-author Amanda B. Payne told UPI in an email.
"The goal of [our] study was to estimate the rate of MIS-C cases in the general population and to estimate the rate of how many people under the age of 21 who were diagnosed with COVID-19 ended up developing MIS-C [and] both estimates were higher among children from racial and ethnic minority groups," said Payne, a researcher with the CDC's COVID-19 Response Team.
MIS-C is a condition in which different body parts can become inflamed, including the heart, lungs, kidneys, brain, skin, eyes or gastrointestinal tract, according to the CDC.
Its symptoms have been compared to another rare childhood disorder called Kawasaki disease and they can cause significant organ damage, the agency said.
This multi-organ inflammation can prove fatal if left untreated.
For this study, the researchers analyzed data on reported cases of MIS-C in children diagnosed with COVID-19 in Connecticut, Georgia, Massachusetts, Michigan, New Jersey, New York and Pennsylvania between April and June of last year.
Across the seven states, there were 248 cases of MIS-C in children ranging in age from 4 to 13, and 133 of them were male, the data showed.
Of the 248 cases, 96, or 39%, were Hispanic or Latino and 75, or 30%, were Black, while 34, or 14% were White and 11, or 4%, were Asian or Pacific Islander.
Race and ethnicity information was unavailable for 32 of the 248 MIS-C cases.
"MIS-C has always been thought to be a rare complication of [COVID-19], and our findings ... confirm this," study co-author Dr. Adrienne G. Randolph told UPI in an email.
"As interventions such as vaccination decrease circulation of [the virus] further, it is expected that the frequency of MIS-C will decrease," said Randolph, a professor of anaesthesia and pediatrics at Harvard Medical School in Boston.
Since the start of the pandemic, children ages 18 and younger have accounted for about 4 million, or 14%, of all COVID-19 cases in the United States, the American Academy of Pediatrics estimates.
However, that number has increased steadily over the past year, with young people accounting for roughly one in five of all new cases nationally, the academy said.
"We do not yet know what causes multi-system inflammatory syndrome in children," Payne said.
However, "[we do know that] long-standing health and social inequities are putting many people from racial and ethnic minority groups at increased risk of exposure, illness, hospitalization, and death from COVID-19," she said.