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

The U.S. recorded more than 705,000 COVID-19 cases Thursday and is currently averaging 586,000 new cases per day -- the highest ever recorded during the pandemic. new federal data shows.

With a total confirmed case count of 58.8 million COVID-19 infections, this means one in approximately every five Americans have tested positive for the virus.

New York City is currently recording the country's highest case rate, followed by New Jersey and New York state

Meanwhile, the U.S. is reporting an average of about 1,200 new COVID-19 deaths per day, up by about 10% in the last week.

The death toll currently stands at 834,000, meaning about 1 in every 393 Americans has died from COVID-19.

-ABC News' Arielle Mitropoulos

The Pfizer-BioNTech COVID-19 vaccine dramatically reduces the risk of teenagers developing MIS-C, a dangerous inflammatory condition, according to a new study from the Centers for Disease Control and Prevention published Friday.

MIS-C is a condition in which different body parts can become inflamed such as the heart, lungs and kidneys. It tends to appear in kids and adolescents two to six weeks after becoming infected with COVID-19.

Researchers looked at children and teens between ages 12 and 18 from 24 hospitals across the country.

They found that the vaccine was 91% against MIS-C. Of the children who were critically ill with MIS-C and required life support, all were unvaccinated.

"No fully vaccinated patients with MIS-C required respiratory or cardiovascular life support, as opposed to 39% of unvaccinated MIS-C patients who did," the authors wrote.

-ABC News' Sony Salzman

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