The U.S. set another record for most daily cases, despite some states not even reporting totals due to the New Year's holiday.

There were a record 275,897 cases reported Saturday, even though seven states did not relay any data, according to The COVID Tracking Project.

"Some states are reporting normally, some are reporting multiple days of data, and almost all are dealing with at least some holiday backlogs," the project said.

The seven-day average for hospitalizations stands at a record 123,689 despite incomplete data. There were 2,367 deaths reported on Saturday, too.

Officials expect numbers to spike after the holidays as people return home from gatherings with family and friends.

Legendary talk show host Larry King, 87, has been hospitalized in Los Angeles for COVID-19, a source close to the King family confirms to ABC News.

"Larry has fought so many health issues in the last few years and he is fighting this one hard too, he's a champ," the source close to the family told ABC News.

King, who hosted "Larry King Live" on CNN for 25 years, revealed in 2017 he had been treated for lung cancer. He suffered a major heart attack in 1987 and the tumor was discovered during an annual checkup. He had an angioplasty in April 2019 and suffered a stroke in 2019 as well.

The host went through unbearable tragedy last year when two of his children died less than a month apart. His son, Andy, died of a heart attack in July and his daughter, Chaia, died of lung cancer in August.

King is hospitalized at Cedars-Sinai Medical Center in LA. The news was first reported by ShowBiz411.

ABC News' Alondra Vale and Josh Hoyos contributed to this report.

After authorizing the Houston Health Department to open the city's first free COVID-19 vaccination clinic on Jan. 2, the call center to make vaccination appointments is already overwhelmed, said Houston Mayor Sylvester Turner on Twitter Saturday.

Turner said at a press conference later in the day that the call center received 250,000 calls by 7:30 a.m. when they only planned to provide 750 vaccinations. They turned to on-site registration to handle all the demand.

Turner plans to open "mega-sites" to provide vaccines in the near future, he said. Staff planned to stay late on Saturday and vaccinate about 1,000 people, the mayor said.

Houston reported 2,334 more cases and eight new deaths on Saturday.

ABC News' Matthew Fuhrman and Abby Shalawylo contributed to this report.

New York has become the fourth state to cross 1 million COVID-19 cases, the governor announced Saturday.

New York joined California, Texas and Florida in hitting that mark. Illinois, at over 975,000 cases, is likely to join those four in the coming days. California has already crossed 2 million cases.

"With 2020 now behind us, we can see brighter days ahead, but to get there quickly, it's going to take all New Yorkers staying smart and staying united," Gov. Andre Cuomo said in a statement. "We have the vaccine, and that is good news, but it will be months before we've reached critical mass, making it as important as ever that we do not let COVID fatigue get the best of us."

The state reported just over 15,000 new cases on Saturday and a percent-positivity rate that has grown to 7.45%. That number was around 1% for much of the summer after being the epicenter for the pandemic in the spring.

There was some good news on Saturday as Cuomo reported there were 72 fewer people hospitalized due to the virus in the state.

Officials continue to fear growing cases in the new year after Christmas and New Year's travel in recent weeks. New York crossed 30,000 deaths earlier this week.

Public Health England does not recommend mixing COVID-19 vaccines from different suppliers, according to the agency's head of immunizations, Dr. Mary Ramsay.

"We do not recommend mixing the COVID-19 vaccines -- if your first dose is the Pfizer vaccine you should not be given the AstraZeneca vaccine for your second dose and vice versa," Ramsay said in a statement Saturday. "There may be extremely rare occasions where the same vaccine is not available, or where it is not known what vaccine the patient received. Every effort should be made to give them the same vaccine, but where this is not possible it is better to give a second dose of another vaccine than not at all."

The clarification comes amid questions over the British government's updated guidance on COVID-19 vaccines, which now says that if individuals who received the first shot go to an immunization site where that same vaccine is not available for a second shot, or if the first vaccine received is unknown, "it is reasonable to offer one dose of the locally available product to complete the schedule."

"This option is preferred if the individual is likely to be at immediate high risk or is considered unlikely to attend again," the guidance adds.

The guidance, which was updated Thursday, also notes that "there is no evidence on the interchangeability of the COVID-19 vaccines although studies are underway," and thus "every effort should be made to determine which vaccine the individual received and to complete with the same vaccine."

Next week, the United Kingdom is set to begin distribution of a COVID-19 vaccine developed by England's University of Oxford and manufactured by British-Swedish pharmaceutical giant AstraZeneca, after the drug was approved Wednesday for emergency supply. Another COVID-19 vaccine developed by U.S. pharmaceutical giant Pfizer and its German partner BioNTech was approved in the U.K. on Dec. 2 and rollout began a week later.

ABC News' Zoe Magee contributed to this report.