By Sharon Bernstein

(Reuters) - When her two-year- started feeling sick early last week, Tiffany Jackson didn't think it might be COVID-19.

No one else in the family was sick. Adrian James just had a bit of a cough. She gave him cough syrup and put a humidifier in his room.

But by Friday he was sweaty and his breathing was labored. Jackson took him to an emergency room in her town of Mt. Vernon, Illinois. Doctors and nurses there did a chest X-ray and swabbed him for COVID - and then airlifted the to Cardinal Glennon Children's Hospital in St. Louis, about 80 miles away.

Jackson followed in a car, her grandmother at the wheel. They made the usually 90 minute-drive in about an hour.

"I didn’t know if he was going to make it or not," Jackson said. "I was very emotional and just very upset."

Her boy is one of nearly 840,000 children the of four to contract COVID-19 in the United States, according to statistics from the United States Centers for Disease Control and Prevention (CDC). Vaccinations against COVID-19 have not been approved for young children, and the United States is being ravaged by a surge of cases driven by the highly contagious Delta variant, which Adrian has.

By late Tuesday night, he was intubated and heavily sedated, wrapped in his baby blanket with his favorite Paw Patrol stuffed animal at hand.

Over the past couple of days, his lungs have been able to do more of the work of breathing, and it is possible that he may be removed from the ventilator soon.

The United States crossed the milestone of 700,000 COVID deaths last week, and concern is growing over the number of infections among children.

Transmission of the virus remains high in every U.S. state except California, CDC data show.

'IT IS SERIOUS'

Adrian, who will be three years next month, had developed pneumonia in his left lung. He was breathing fast, trying to gulp air with 76 respirations per minute, nearly twice the normal 40, Jackson said.

At the hospital, doctors and nurses wearing masks, face shields and protective gowns sedated him and put him on a breathing tube attached to a ventilator in the intensive care unit.

Jackson has been sleeping on a couch in his room in the ICU.

Jackson doesn't know how her boy contracted the virus. She had COVID last summer; no one else in the family caught it at that time.

Jackson is not vaccinated against COVID-19 because she has a rare auto-immune disorder called Guillain-Barre syndrome contracted as a result of a flu shot when she was . The syndrome, which is incurable, causes nervous system damage.

Adrian's father, who is home with their younger in Illinois, received one dose of a COVID vaccine but not the second dose, she said. Maybe, she thinks, someone at work passed it to him, although everyone in the factory where he is employed is supposed to wear masks and practice physical distancing.

Jackson, 21, is profoundly grateful for the care her has received. She is beginning to believe that it will save his life.

And she hopes that Adrian's story will help people understand what it could mean to the pass the virus to young children and to people with vulnerable immune systems.

"I just want people to realize it is serious," she said.

(Reporting by Sharon Bernstein in Sacramento, California. Additional reporting by Callaghan O'Hare in St. Louis. Editing by Donna Bryson, Robert Birsel)