The rate of infections with the coronavirus in adolescents aged 12 to 17 years is about twice that in children aged 5 to 11 years, according to an analysis released Monday by the Centers for Disease Control and Prevention.
The finding is based on a review of 277,285 confirmed cases in children from March to September, when most schools in the nation offered only remote learning or were closed.
Children often have mild symptoms, if any at all, so some researchers have suggested that the low numbers of confirmed cases in children result from a lack of testing.
The number of children tested increased to over 320,000 in mid-July from 100,000 on May 31. By July, the incidence of infected children had risen to 37.9 per 100,000 from 13.8.
Along with other evidence about the incidence of coronavirus infections in those under age 19, the new figures suggest “that young persons might be playing an increasingly important role in community transmission,” the authors wrote.
The number of tests and the incidence of infections decreased after July, but may again be rising, the researchers added.
The number of children infected during the study period varied by age. The weekly incidence among adolescents was 37.4 per 100,000, compared with 19 per 100,000 among younger children.
Children who had underlying conditions were more likely to become severely ill, the analysis also found. Among school-aged children who were hospitalized, admitted to an intensive care unit, or who died, 16 percent, 27 percent and 28 percent, respectively, had at least one underlying medical condition, the researchers reported.
Deaths among children were rare, but Black and Hispanic children were more likely to be hospitalized or admitted to an I.C.U., the C.D.C. reported.