Los Angeles County saw over 43,000 new cases in one day, a new record, health officials announced Friday.

This beats Thursday's previous record high of 37,000.

There are 2,902 people with COVID-19 currently hospitalized in the county, according to health officials.

L.A. County Director of Public Health Dr. Barbara Ferrer noted that vaccinated individuals are "between 10 and 30 times less likely to need hospital care than those unvaccinated."

"Every resident can also do their part to protect our healthcare personnel and hospitals. Please get vaccinated or boosted as soon as possible if eligible," she said in a statement.

-ABC News' Alex Stone

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 American Medical Association, the nation’s largest association of physicians, has criticized the Centers for Disease Control and Prevention's new quarantine and isolation guidance for COVID-19, saying the recommendations "are risking further spread of the virus."

The CDC updated its guidelines on Dec. 27, saying asymptomatic people who test positive for COVID-19 should self-isolate for five days rather than 10.

"The American people should be able to count on the Centers for Disease Control and Prevention (CDC) for timely, accurate, clear guidance to protect themselves, their loved ones, and their communities. Instead, the new recommendations on quarantine and isolation are not only confusing, but are risking further spread of the virus," the American Medical Association's president, Dr. Gerald E. Harmon, said in a statement Wednesday night.

Harmon referenced data cited by the CDC in its rationale for shortening the isolation period, which estimates 31% of people remain infectious five days after a positive COVID-19 test, suggesting that data proves thousands of Americans could return to their lives while still infected.

"With hundreds of thousands of new cases daily and more than a million positive reported cases on January 3, tens of thousands -- potentially hundreds of thousands of people -- could return to work and school infectious if they follow the CDC’s new guidance on ending isolation after five days without a negative test," Harmon said. "Physicians are concerned that these recommendations put our patients at risk and could further overwhelm our health care system."

Harmon said a negative COVID-19 test should be required for ending isolation after a positive test, as reentering society without knowing whether an individual is still positive ultimately risks further transmission of the virus.

Although test availability remains an issue nationwide, Harmon also called on the Biden administration to ramp up production and distribution of tests, adding that "a dearth of tests at the moment does not justify omitting a testing requirement to exit a now shortened isolation."

-ABC News' Arielle Mitropoulos