Last month, as Delta surged, the incidence of Covid in children rose from earlier in the summer — reaching 16.2 cases per 100,000 children ages 4 and under; 28.5 cases per 100,000 children ages 5 to 11; and 32.7 cases per 100,000 children ages 12 through 17.
That rate represented a sharp spike from a June low of 1.7 per 100,000 children ages 4 and under; 1.9 cases per 100,000 children ages 5 to 11; and 2.9 per 100,000 children between ages 12 and 17. It was still below the peak incidence of cases among children last January.
The proportion of Covid patients under 17 who were admitted to intensive care units ranged from 10 to 25 percent from August 2020 through last June, and hovered at 20 percent by July 2021, according to the C.D.C. study.
In a second study, researchers analyzed data from the Covid-Net surveillance network, which includes information on hospitalizations in 99 counties across 14 states.
Over the course of the pandemic — or from March 1, 2020, to Aug. 14, 2021 — there were 49.7 Covid-related hospitalizations per 100,000 children and adolescents, the researchers found.
But the weekly rates have been climbing since July. During the week ending Aug. 14, there were 1.4 Covid-related hospitalizations for every 100,000 children, compared to 0.3 in late June and early July. (That remains slightly below the peak weekly rate of 1.5 hospitalizations per 100,000 children, in early January 2021, in the post-holiday wave of cases.)
Hospitalization rates have increased most sharply for children who are 4 or younger. In the week ending Aug. 14, there were 1.9 hospitalizations per 100,000 children in that age group, nearly 10 times as many as in late June.