COVID-19 updates: Classes in Chicago canceled for 4th day

Mayo Clinic said it will lay off about 1% of its staff for failing to get at least one dose of the COVID-19 vaccine by a company deadline. 

"While Mayo Clinic is saddened to lose valuable employees, we need to take all steps necessary to keep our patients, workforce, visitors and communities safe. If individuals released from employment choose to get vaccinated at a later date, the opportunity exists for them to apply and return to Mayo Clinic for future job openings," Mayo Clinic said in a statement to ABC. 

Last October, Mayo Clinic had set a Jan. 3 deadline for all employees to get at least their first vaccine dose or face dismissal. 

The health care organization said the number of staffers being let go was "comparable to what other health care organizations have experienced in implementing similar vaccine requirement programs."

Mayo Clinic employs about 73,000 people, according to its website.

The FDA is warning people not to swab their throats as part of an at-home COVID-19 test.

In a statement obtained by ABC News, the FDA said that is not how the tests were designed and it could pose a safety concern.

"The FDA advises that COVID-19 tests should be used as authorized, including following their instructions for use regarding obtaining the sample for testing," the statement said.

Social media posts promoting at-home COVID-19 rapid test swabbing techniques claim that throat swabs collect a better sample. However, this hasn't been proven for currently authorized tests.

- ABC News' Sony Salzman

President Joe Biden announced Tuesday afternoon that he was doubling the federal government's purchases of Pfizer's COVID-19 antiviral pill, from 10 million to 20 million treatment courses.

"They’re a gamechanger and have the potential to dramatically alter the impact of COVID-19, the impact it's had on this country and our people,” Biden said.

He also warned that those who remain unvaccinated "will die" during the ongoing omicron surge.

“So there's no excuse, no excuse, for anyone being unvaccinated,” Biden said.

-ABC News' Ben Gittleson

Data released by the Centers for Disease Control and Prevention from the weekend shows that the U.S. is now averaging nearly half a million new cases a day.

About a year ago, the U.S. was reporting an average of about 216,000 new cases a day. However, compared to last winter, hospital admissions and daily deaths are notably lower.

Over the last week, the U.S. reported more than 3.4 million new cases -- roughly averaging out to nearly six Americans testing positive every second.

-ABC News' Arielle Mitropoulos