The latest data from Maricopa County Public Health shows one in four COVID-19 cases are among children and one in six cases are among children under 12 who are ineligible for any of the vaccines against the virus.

"We have never seen that in this pandemic," said Dr. Rebecca Sunenshine, medical director of MCPH, during a news conference Aug. 30. "We just weren't seeing as many cases in children previously because the original strain of COVID[-19] did not infect children as much as it infected older adolescents and older people. There is something about the delta strain that it affects children just as much as other people. What we are seeing is a dramatic rise in children."

Sunenshine said the number of cases in children was on the rise with the delta variant, but it increased dramatically when school began across Arizona.

"When you have a whole bunch of people, particularly people who are under 12 and by definition unvaccinated, when you put them all together—it is going to increase rapidly," she said. "And that is exactly what we saw."

According to the county's COVID-19 dashboard for schools, Maricopa County remains in a high-transmission rate with test positivity at 11% as of Aug. 30.