Texas attorney general Ken Paxton waded into a battle between the city of Austin and Gov. Greg Abbott Friday over whether the city's four-day late-night indoor dining shutdown should be allowed.

Austin's ban, which was set to run between 10:30 p.m. and 6 a.m. from Dec. 31 until Jan. 3, was upheld by a judge on Thursday. Hours later, at 7:39 p.m. local time on New Year's Eve, the governor released a statement on Twitter telling restaurants to stay open.

Paxton backed the governor on Friday and called for the Texas Supreme Court to halt enforcement of the ban. "We cannot have local declarations conflicting with Gov. Abbott’s clear order," he said in a statement. "I will continue to fight for Texans, small businesses and for an open economy."

-ABC News' Jenna Harrison contributed to this report.

The United States surpassed 20 million coronavirus cases on New Year's Day, with 20,007,149 infections, according to data from Johns Hopkins University.

In different terms, 1 out of every 16 Americans has tested positive for COVID-19.

As the nation's third COVID wave continues, California has emerged as a major epicenter of the U.S. outbreak and at least three states have reported cases of the new COVID variant, which originated in the U.K. Health experts believe it to be more transmissible than the old variant, although it is not thought to be more deadly.

According to JHU, 346,408 Americans had died of the virus as of Friday.

Sen. Mitt Romney criticized the Trump administration's vaccine rollout in a statement he released Friday, writing: "when something isn’t working, you need to acknowledge reality and develop a plan—particularly when hundreds of thousands of lives are at stake."

Relying on states in lieu of developing a federal vaccination plan is "as incomprehensible as it is inexcusable," Romney wrote, and offered up his own suggestions as examples of the brainstorming he said ought to be happening in Washington.

The government should enlist every medical professional not currently delivering care, such as retired veterinarians, combat medics and corpsmen and medical students, to administer vaccines, Romney suggested, noting that they could be paid using the funding Congress has appropriated for states. Additionally, schools could serve as vaccine sites and vaccinations could be scheduled for specific days according to a person's priority category and birthdate.

While public health professionals will easily point out errors in his plan, he said, the nation needs new strategies based on "experience, modeling and trial," especially as the U.S. begins vaccinating more complex populations.

"We are already behind," Romney added. "Urgent action now can help us catch up."

-ABC News' Trish Turner and Chris Howell contributed to this report.

Construction on a 30-bed emergency field hospital is slated to start in western North Carolina Friday, as COVID-19 cases in the state continue to rise.

The facility, which is being built next to Caldwell Memorial Hospital, will treat COVID patients who aren't sick enough to need a ventilator and is meant to relieve pressure on five health systems in the region.

As of Thursday, 3,472 people were hospitalized because of the virus, according to the state health department.

The Centers for Disease Control and Prevention updated its guidelines for people with underlying health conditions planning to take a COVID-19 vaccine.

They CDC said that adults with underlying medical conditions -- who are more at risk of becoming seriously ill from COVID-19 -- can receive a vaccine against the virus as long as they have not had a severe allergic reaction to any of the ingredients in it.

The new guidelines state that people with HIV and those with weakened immune systems due to other illnesses or medication should be aware that information about the safety of COVID-19 vaccines for their group is not yet available. While people with HIV were included in clinical trials, more data is required to provide safety guidelines regarding the effects a vaccine could have on them. The same is true for people with autoimmune conditions.

People who have previously had Guillain-Barre syndrome or Bell’s palsy may receive a COVID-19 vaccine, though experts are still acquiring more data about their groups as well.

The CDC added that people should continue to follow coronavirus health measures -- such as wearing a mask and staying 6 feet away from others -- after receiving the shot, as experts have more to learn about the protection that COVID-19 vaccines provide under real-life conditions.