Children under age 12 aren’t yet eligible to be vaccinated, and vaccination rates for those between 12 and 17 remain relatively low, according to data compiled by the American Academy of Pediatrics. Although children are much less likely than adults to develop severe Covid-19 or die from the virus, recent data from the Department of Health and Human Services show pediatric hospitalizations for Covid-19 are at the highest point since the agency began tracking them last year, driven by states that have been hit hard by the Delta variant.

Children’s hospitals are bracing for even more cases as schools reopen. They are hiring more nurses, reworking discharge protocols, speeding up room cleanings, laying contingency plans to expand bed capacity and preparing staff for an uptick in multisystem inflammatory syndrome in children, or MIS-C. A rare condition that can occur several weeks after Covid-19 infection, MIS-C can lead to organ damage or even death without the proper diagnosis and management.

It isn’t clear whether the Delta variant is making kids sicker than they would have been if infected with previous strains. Some pediatricians believe that is the case because of the severity of the cases they have treated. Other pediatricians don’t think Delta is causing more severe Covid-19 in children than earlier variants. But with Delta spreading widely, the number of children hospitalized with Covid-19 far outstrips anything they saw in the past.