(CBS News) – More than four million children have been infected with COVID-19 in the U.S. since the start of the pandemic, according to the American Academy of Pediatrics. With the highly infectious Delta variant spreading across the country, doctors worry about that number continuing to climb.

Dr. Fatma Levent specializes in pediatric infectious diseases in Orlando, where COVID-19 cases are on the rise. “Now what we’re seeing is younger children, younger adults, are getting the infection and bringing it to their families.”

As the powerful Delta variant sweeps the country, Dr. Levent says it’s affecting children more than previous strains. And more of them are ending up in the hospital. “When they get it, it’s usually mild. However, they can get hospitalized, they can get pneumonia, and other complications,” Dr. Levent says.

In June, Katia Tejada’s daughter Kaithlyn Merejo contracted COVID-19. “I was scared, I was panicking because she said she had a headache, her body, it was in pain,” Katia says.
The 15-year-old is unvaccinated and spent three days in the hospital when the infection led to pneumonia. “It was a bit scary for me. My throat hurt a lot,” Kaithlyn said. She thinks she was infected at a party where people were unmasked. She’s on the mend now and the family plans to be much more cautious in the future.

In Florida, about 90% of seniors are vaccinated. But among children, the number is lagging far behind. The CDC says just over 30% of kids between 12 and 17 have had their shots, slightly below the national average. Mississippi’s rate is just 12%, the lowest in the nation.
“In this phase of the pandemic there’s really two life choices: it’s to vaccinate or you’re going to get COVID,” says Dr. Jennifer Bryan from the Mississippi State Medical Association.

The American Academy of Pediatrics says severe COVID is still rare among children but that more research is needed on the possible long-term effects of the virus.