The incidence of COVID-19 in individuals aged 0 to 24 years increased since summer 2020 with weekly incidence higher in each successively increasing age group, according to a report published in the weekly Morbidity and Mortality Weekly Report by the Center for Disease Control and Prevention (CDC). Findings suggest that young adults may contribute more to the community transmission of SARS-CoV-2 than younger children.

In this report, researchers from the CDC examined electronic laboratory reporting data submitted from 44 states, the District of Columbia, 2 territories, and 1 freely associated state to analyze trends in COVID-19 incidence in individuals aged 0 to 24 years between March 1, 2020, and December 12, 2020. Children, adolescents, and young adults were stratified into 5 age groups: aged 0 to 4 years, 5 to 10 years, 11 to 13 years, 14 to 17 years, and 18 to 24 years to align with educational groupings. Trends in these groups were compared with adults 25 years of age and older.

Of the 2,871,828 cases of COVID-19 reported in the United States, 57.4% occurred among young adults aged 18 to 24 years, 16.3% in adolescents aged 14 to 17 years, 7.9% in children aged 11 to 13 years, 10.9% in children aged 5 to 10 years, and 7.4% in children aged 0 to 4 years.

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There was an increase in reported weekly COVID-19 incidence and percentage of positive SARS-CoV-2 test results with spikes in early summer, followed by a decline and then steep increase in October through December among all age groups. Compared with older age groups, children aged 0 to 10 years consistently had lower incidence and percentage of positive SARS-CoV-2 test results. However, incidence among young adults aged 18 to 24 years was “higher than that in other age groups throughout the summer and fall, with peaks in mid-July and early September that preceded increases among other age groups,” the researchers stated.

The timing of COVID-19 incidence peaks in young adults predating peaks in younger and older populations suggests that young adults, rather than children, may be a source community transmission. This finding was further highlighted when evaluating risk for transmission in school settings. Among counties where K-12 education was offered in person, the incidence of COVID-19 was similar to counties that offered only virtual or online education (401.2 vs 418.2 cases per 100,000 persons, respectively).

The COVID-19 incidence was likely underestimated, since testing among children and adolescents was lower than that for adults. In addition, the study was limited due to incomplete data on race/ethnicity, symptom status, underlying conditions, and outcomes.

“CDC recommends that K-12 schools be the last settings to close after all other mitigation measures have been employed and the first to reopen when they can do so safely,” the researchers concluded.


Leidman E, Duca LM, Omura JD, Proia K, Stephens JW, Sauber-Schatz EK. COVID-19 trends among persons aged 0-24 years – United States, March 1-December 12, 2020. MMWR Morb Mortal Wkly Rep. 2021;70(3):88-94. doi:10.15585/mmwr.mm7003e1