More than 300 children with COVID-19 are in Ohio hospitals, including Dayton Children's Hospital, where workers are seeing a significant increase in pediatric COVID-19-related hospitalizations.

Dr. Vipul Patel, chief of pediatric intensive care at Dayton Children's, told ABC News the ICU is now busier than at any other point in the pandemic.

COVID-19 is only exacerbating previously existing health issues for many children, Patel explained, adding that many parents are shocked to see their children become so sick, and some families have even expressed regret for not vaccinating their kids. Nationwide, about 35% of eligible children (ages 5 to 17) are fully vaccinated, according to federal data.

Dayton Children's respiratory therapist Hillary O’Neil said it's been particularly difficult to see children who are too young to understand what is happening sick and scared.

“You can see it in the faces of kids that can’t talk -- their eyes get really big and they, we watch them struggle to breathe,” O’Neil said. “Then on top of that we watch their parents struggle to watch their child, and that is sometimes just as hard as watching the kids.”

Jackie Kerby, whose baby, Enaeshya, is hospitalized with COVID-19, told ABC News, "She’s getting these fevers in the night, and they’re not coming down. … I am terribly scared."

Across the U.S. more than 5,000 children are currently hospitalized with a confirmed or suspected case of COVID-19, according to federal data. On average, hospital admissions among children have quadrupled over the last month.

-ABC News' Arielle Mitropoulos, Kayna Whitworth

New York state's COVID-19 cases are falling after experiencing a major surge over the holidays, according to state data.

New York recorded 60,374 new cases in the last 24 hours -- an improvement from New Year's Day when 85,476 daily cases were reporting during a spike in testing demands.

The Supreme Court has issued a stay of the vaccine-or-test requirement imposed on private businesses with at least 100 employees by the Occupational Safety and Health Administration.

In a 6-3 ruling, with the three liberal justices dissenting, the court finds likelihood the challengers will prevail and that OSHA exceeds its authority.

At the same time, the justices voted 5-4 to allow the Biden administration to require health care workers at facilities that treat Medicare and Medicaid patients to be vaccinated, subject to religious or medical exemptions.

-ABC News' Devin Dwyer

About 8,000 of Delta Air Lines' 75,000 employees had COVID-19 over the last four weeks, Delta CEO Ed Bastian told CNBC.

"Good news is that they were all fine. There's been no significant issues," he said.

"But it's knocked them out of the operation" amid the busiest travel season in two years, he said.

United CEO Scott Kirby said Tuesday that around 3,000 of United workers have COVID-19 right now.

Across the U.S., 3,783 TSA employees are currently at home with COVID-19, the agency said.

-ABC News' Mina Kaji, Sam Sweeney

Spain has reported more COVID-19 reinfections in a recent span of two weeks than it has during the rest of the pandemic, according to the latest data from a Spanish public health research institute.

Data from the Carlos III Health Institute shows there were 20,890 repeat infections reported in Spain from Dec. 22, 2021, to Jan. 5, 2022. That figure tops the 17,140 reinfections reported in the European country from the start of the pandemic in March 2020 to Dec. 22, 2021. The data includes confirmed, probable and possible cases.

Alfredo Corell, an immunology professor at Spain's University of Valladolid, told Spanish news site NIUS that the rising number of reinfections were due to the new and highly transmissible omicron variant.

"Prior to this variant, reinfections were anecdotal at the global level," Corell told NIUS. "Omicron has changed this paradigm."

In southern Africa, where the variant was first identified in November, preliminary research suggests that omicron is three times more likely to cause reinfections compared to other known variants of the virus, including the highly contagious delta. However, symptoms of reinfected individuals appear to be mild, according to Anne von Gottberg, a microbiologist at South Africa's National Institute for Communicable Diseases who is studying omicron.

"Previous infection used to protect against Delta," von Gottberg said during a press briefing on Dec. 2. "But now, with Omicron, that doesn't seem to be the case."