Hospitalization rates for young children with COVID-19 have hit a record high, the Centers for Disease Control and Prevention announced Friday.

“While children still have the lowest rate of hospitalization of any group, pediatric hospitalizations are at the highest rate compared to any prior point in the pandemic,” CDC director Rochelle Walensky said. “Sadly, we are seeing the rates of hospitalization increasing for children 0 to 4, children who are not yet currently eligible for COVID-19 vaccination.”

According to CBS News, the hospitalization rates for kids under 5 have reached more than 4 cases per 100,000 children—an increase from 2.5 per 100,000 prior to mid-December. However, Walensky told reporters Friday that some of the infected youngsters were admitted to hospitals for non-COVID-related issues; it wasn’t until later that physicians confirmed they had contracted the disease.

“It may very well be that there are just more cases out there and our children are more vulnerable with more cases around them,” Walensky added

As of now, the COVID vaccines have not been authorized for children under 5. The CDC reports the COVID hospitalization rate for children 5 to 17 is four times lower than what’s been reported among kids 4 and younger. The CDC reports about 50 percent of kids ages 12 to 18 are fully vaccinated, while 16 percent of kids between 5 to 11 are fully vaccinated. Walensky also pointed out that the majority of children who were hospitalized with COVID have yet to receive the jab.

“Hospitalizations are going up. There’s no reason to think that they wouldn’t go up in children … children don’t seem to be as unsusceptible to this as they have been to earlier strains ...” George Rutherford, professor of epidemiology and pediatrics at UCSF, told BuzzFeed News“In 2020 COVID was the seventh leading cause of death in children in the United States. It is a big deal. And people who pooh-pooh it and say ‘oh, its no big deal are blind to facts.”