Chicago Public Schools canceled its Wednesday classes after the Chicago Teachers Union voted against in-person learning amid a wave of COVID-19 cases.

All classes, both in-person and virtual, and all after-school activities have been cancelled.

"I understand your frustration and deeply regret this interruption to your child's learning," said Pedro Martinez, chief executive of the schools. "We want out children back in their classrooms as soon as possible and will continue working with the CTU to reach an agreement that addressed their concerns and that is in the best interest of all in our CPS community, especially our children."  

About 88% of the union's leadership and 73% of members voted on Tuesday to return to remote education, the union said in a statement.  

"To the parents and guardians of this city, we want you to know that when you put your children in our care we put their well-being and safety first," the union said in a statement. "We fight for your children like they are our own, because they are. As this pandemic continues, we will do everything in our power to ensure that our classrooms are the safest and healthiest places for your children to learn, thrive and grow."

Teachers were being locked out of their Google Classrooms, the union said on Twitter.

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