As tens of thousands of kids return to school this week in the Bay Area, there is growing evidence that the delta variant may be more dangerous for children than prior variants.
Doctors at Lucile Packard Children's Hospital Stanford are seeing a change in the number of kids with COVID.
"We are certainly seeing an increase in the number of children who are hospitalized in recent weeks," said Dr. Grace Lee, a pediatrics professor at Stanford University's School of Medicine.
Lee said a majority of kids hospitalized with COVID have the delta variant.
"We do know it is far more transmissible -- maybe a thousand fold higher viral load, so we do anticipate transmission will be greater," she said.
Across the nation, the number of kids getting COVID is increasing. According to the American Academy of Pediatrics, 16 states including California now have a total of more than 100,000 pediatric COVID cases.
While most children recover within a week, new research is showing that kids who are infected are also at risk of becoming "long haul" COVID patients.
"Characteristically what we're seeing in children reflects what we're seeing in other ages -- fatigue for months, loss of smell and difficulty concentrating," said Dr. John Swartzberg with UC Berkeley's School of Public Health.
Swartzberg also said in some rare cases children who have had COVID have developed an inflammatory response impacting their joints, brain and heart. All this is even more troubling when considering only kids 12 and older currently qualify for the vaccine.
Infectious disease experts said they expect the FDA to approve a COVID vaccine for children under the age of 12 by the end of the year.
But until all kids can get a shot, they said masks at school and a community of vaccinated adults is the best defense against COVID.