As the Delta variant spreads across the US, COVID-19 cases are back on the rise, especially in children. 

According to a new statement by the American Academy of Pediatrics (AAP), 72,000 new cases of COVID-19 were reported in children in the US. That’s about an 85 percent increase from the 39,000 new cases reported in kids the week before. Nearly 4.2 million children in the country have tested positive for COVID-19 since the onset of the pandemic, and recent figures show that youth now represent 19 percent— or nearly one in five of all new cases. Children under the age of 12 still cannot get vaccinated in the US.

Despite the rising case counts, severe disease in kids is still statistically unlikely. The AAP reports that from self-reported data of 43 states, only 0.26 percent of all COVID-19 deaths are in children. Seven states have yet to report a single child death. Data from 23 states also show that less than two percent of child COVID-19 patients end up in the hospital (though, the AAP also notes that the definition of “child” in the data differs state by state). 

[Related: Pfizer and Moderna are studying their COVID vaccines in kids as young as 6 months.]

Though the percentage of severe illness in children seems quite low, pediatricians and epidemiologists warn that the virus’s potential impacts on children should not be taken lightly. For example, while persistent long-term effects of COVID-19 are well documented in adults, children can get “long COVID” too. 

“You can get COVID at 18 months of age,” Audrey John, chief of pediatric infectious diseases at the Children’s Hospital of Philadelphia, told STAT in June. “Maybe you can’t tell us that you have a little brain fog. Maybe you can’t tell us that you just don’t feel great. But whether those kids grow like they’re supposed to, develop language like they’re supposed to, go on to be successful in school like they’re supposed to—we’re not going to learn for a long time.”

Nature reported that symptoms such as headache, fatigue, and heart palpitations can persist for months in children after infection, even if their initial symptoms of COVID-19 are not very severe. Data released by the UK Office of National Statistics also showed that about 10 percent of children aged 2–11 years and 13 percent aged 12–16 years reported at least one lingering symptom five weeks after a positive diagnosis. 

Both Pfizer and Moderna are currently conducting trials for their mRNA vaccines in children under 12, and both companies are expected to report their findings for the 5 to 11 year old cohort in September. But it’s unlikely that the majority of kids will receive shots before the start of the impending school year. As children reenter the classroom this fall, the AAP recommends that “everyone older than age 2 wear masks, regardless of vaccination status.”

[Related: How should parents with unvaccinated kids handle the CDC’s new mask guidelines?]

Of course, as the country edges towards dosing its youngest constituents, vaccine safety is of utmost concern. Peter Marks, the director of the Center for Biologics Evaluation and Research at the US Food and Drug Administration told Bloomberg “as we get down below age 12, we’re going to be looking even more critically at the safety data, so that we make sure that we’re very convinced that the children are getting as much direct benefit as they possibly can.” 

At a White House briefing in May, Director of the National Institute of Allergy and Infectious Diseases Anthony Fauci said the US “will have enough information regarding safety and immunogenicity to be able to vaccinate children of any age” by the first quarter of 2022. A Biden administration official also told Bloomberg that the US government has already purchased 65 million doses in anticipation of vaccinating the under-12 cohort.

The only shot currently approved for children aged 12 to 17 in the US is the Pfizer-BioNTech mRNA vaccine, and the US Centers for Disease Control and Prevention urges everyone 12 years and older to get their dose(s). Children are a huge demographic in the US—there are over 73 million children in the country, or about 22 percent of the population. Vaccinating kids would be a huge step towards achieving much-needed herd immunity.