About half of COVID-19 patients hospitalized in New York City were originally admitted for other reasons, Gov. Kathy Hochul said.

Across the state, 42% of COVID-19 patients entered hospitals for reasons unrelated to the virus, such as a car accident, and only learned they were positive during their stays, Hochul said during a press conference Friday.

This is the first time that New York has differentiated between patients who go to hospitals to get care for COVID-19 and those who seek out care for other issues but test positive upon arrival.

Hochul also asked New Yorkers who have mild symptoms to not got to emergency rooms to get tested or treated because many hospitals are currently understaffed.

"If you're an adult with very minor symptoms, you can handle a runny nose. You can handle the throats being a little sore, a little bit of a cough. Just treat as if you would the flu, all the protocols," she said. "But please don't overburden our emergency rooms."

Hochul added that nearly 20% of all emergency rooms in the state are made up of people who are there only to get tested for COVID-19.

-ABC News' Will McDuffie

The White House and USPS have finalized a plan to mail out 500 million free at-home rapid COVID-19 tests to Americans, a source briefed on the plan told ABC News.

It comes as the first contract to produce the tests was awarded to a testing company Thursday night, a White House spokesperson confirmed.

The main issue that was delaying the finalization of the plan was whether or not USPS can retain 40,000 temporary holiday season workers to help deliver the tests.

However, it's not clear how many tests will be available from the first contract or how exactly USPS will deliver them. The White House has been vague on the timeline and has yet to launch a website through which Americans can order the tests.

The USPS-White House deal was first reported by The Washington Post.

-ABC News' Lucien Bruggeman, Cheyenne Haslett and Sasha Pezenik

COVID-19 vaccines can cause temporary changes to menstrual cycles, a new study from Oregon Health and Science University suggests.

Researchers looked at nearly 4,000 women who use Natural Cycles, a Food and Drug Administration-approved birth control app.

They found that some women who received COVID-19 vaccines experienced changes, with the most common being periods starting late by about one day.

However, the effects were temporary with a normal menstrual cycle returning within one or two months after getting the shot.

The team emphasized the findings do not mean COVID-19 vaccines have an impact on current or future fertility.

-ABC News' Katie Kindelan

The COVID-19 hospitalization rate for U.S. children between ages 0 and 4 has hit a record high, according to new data from the Centers for Disease Control and Prevention published Friday.

For the week ending Jan. 1, 2021, the hospitalization for young kids was 4.3 per 100,000.

"While children still have the lowest rate of hospitalization, pediatric hospitalizations are at their highest point compared to any other point prior in the pandemic," CDC director Dr. Rochelle Walensky said during a media call with reporters Friday.

Children under age 5 are currently not eligible to be vaccinated.

As negotiations between city officials and the teacher’s union continue, Chicago Mayor Lori Lightfoot announced on Twitter Sunday night that classes will be canceled for a fourth day, on Monday.

"Out of fairness and consideration for parents who need to prepare, classes will be canceled again Monday," she tweeted.

Lightfoot said that though they have been negotiating hard, there has not been "sufficient progress" for a return to class to be announced.

"We will continue to negotiate through the night and will provide an update if we have made substantial progress," she wrote.

Chicago Public Schools, the nation’s third-largest school district, has been in talks with the teachers’ union over remote learning and COVID-19 safety protocols.

Amid the rise in COVID-19 cases due to the omicron variant, the Chicago Teachers Union wants the option of returning to remote learning, and most members are refusing to teach in person until an agreement is reached.