COVID-19 updates: More than 10,000 new deaths reported in US in 1 week

The most populous county in Washington state will implement COVID-19 vaccine and testing requirements for indoor dining, large outdoor events and other activities. 

Starting Oct. 25, proof of COVID-19 vaccination will be required for everyone ages 12 and up to enter indoor establishments, including restaurants, bars, gyms and movie theaters, and attend outdoor events with more than 500 people in King County, home to Seattle, officials announced Thursday.

Those who are not vaccinated must show proof of a negative PCR COVID-19 test in the last 72 hours or take a rapid test on site prior to entry. 

"We are at a critical point in this pandemic, with high levels of new COVID-19 cases and hospitalizations, and no certainty as to what will follow the Delta variant," King County Executive Dow Constantine said in a statement. "Vaccination is our best shield against this deadly virus." 

Over 85% of King County residents have received at least their first dose of the COVID-19 vaccine, according to Constantine.

Lumen Field, home of the NFL's Seattle Seahawks, already required vaccination or a negative test, while the MLB's Seattle Mariners said last week they would institute the same guidelines should they make the playoffs.

Two dozen state attorneys general are threatening legal action against the federal government over a COVID-19 vaccine mandate for private businesses.

A week after President Joe Biden announced that the Occupational Safety and Health Administration will create a rule that will require roughly 80 million workers nationwide to be vaccinated or undergo weekly testing, 24 Republican state attorneys general warned in a letter addressed to the president that they "will seek every available legal option" if the mandate is implemented.  

The letter, which called the plan "disastrous and counterproductive" and debated its legality, was signed by the attorneys general of Alabama, Alaska, Arizona, Arkansas, Florida, Georgia, Indiana, Kansas, Kentucky, Louisiana, Mississippi, Missouri, Montana, Nebraska, New Hampshire, North Dakota, Ohio, Oklahoma, South Carolina, South Dakota, Texas, Utah, West Virginia and Wyoming.

Earlier this week, U.S. Surgeon General Vivek Murthy defended Biden's vaccine plan in an interview with "This Week" anchor George Stephanopoulos.

"The requirements that he announced are not sweeping requirements for the entire nation," Murthy said. "These are focused on areas where the federal government has legal authority to act."

The Centers for Disease Control and Prevention’s weekly ensemble forecast, an average of several models, predicts that the number of new daily hospital admissions will likely drop.

The ensemble forecast predicts "5,000 to 15,300 new confirmed COVID-19 hospital admissions likely reported on October 11." The current seven-day average is 11,165 new hospitalizations per day.

-ABC News' Brian Hartman

In an open letter, Pfizer CEO Albert Bourla is making the case for his company's vaccine booster shot, one day before an FDA advisory committee meets to debate and vote on the issue. 

Bourla underscored the "strong immune response after the booster dose" and vowed that Pfizer has "stayed true to our commitment of full transparency without selectively cherry-picking data."  

Bourla also addressed international concerns over boosters for all potentially detracting from access to first doses in developing countries. 

"Some people and organizations have raised concerns that the approval of boosters will divert doses dedicated to the low- and middle-income countries and redirect them to the high-income countries. And they use this argument to claim that boosters should not be approved. I disagree," Bourla wrote.  

"No commitments already made by Pfizer to a country will change if boosters are approved," he wrote. 

-ABC News' Sasha Pezenik