U.S. Surgeon General Jerome Adams tweeted Thursday morning that his wife had been admitted to a hospital because of complications with her cancer treatment. He said he wasn’t allowed to visit her because of COVID-19-related restrictions.

Adams’ wife, Lacey Adams, was first diagnosed with metastatic melanoma in 2018.

“I’m hoping she doesn’t have to spend New Year’s in a hallway because the beds are full,” Adams tweeted.

ABC News’ Ben Gittleson and Tom Dunlavey contributed to this report.

At least 342,734 lives have been lost to COVID-19 in the U.S., representing approximately 18.9% of the total global death toll of 1.8 million people.

One in every 965 Americans has now died from the virus, according to ABC News’ of data compiled by the COVID Tracking Project.

The U.S. death toll is 114 times the total lives lost on Sept. 11, 2001, and just over half the total number of deaths that were recorded in U.S. during the 1918 influenza pandemic.

At least 19.7 million Americans have tested positive for COVID-19 in the 345 days since the Centers for Disease Control and Prevention confirmed the first U.S. case on Jan. 21.

That means about 1 in every 16 Americans has contracted the virus.

ABC News' Arielle Mitropoulos contributed to this report.

The oldest resident of Massachusetts, 112-year-old Hazel Plummer, received her first dose of the vaccine on Wednesday.

Plummer was among the 49 residents and 50 employees at the Life Care Center of Nashoba Valley, a nursing home in Littleton, Massachusetts, to do so.

The Life Care Center of Nashoba Valley suffered from the coronavirus outbreak in the spring but “was free of COVID-19 by the end of May,” the facility said.

ABC News’ Arielle Mitropoulos contributed to this report.

In Wuhan, China, where COVID-19 was first identified in December 2019, small crowds gathered to take in a fireworks display and ring in 2021.

Wuhan was the first epicenter of the pandemic, but the central Chinese metropolis of 11 million emerged out of lockdown in mid-April and has not had a reported case since May.

In New York City, no New Year’s revelers will be gathering in Times Square to watch the ball drop this year.

New York City Mayor Bill de Blasio said this is "the most moving New Year's Eve," but urged New Yorkers to "watch on TV. Don't go down there."

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.