California recorded 30,851 new cases on Tuesday, bringing the state's case total to over 1.42 million.

The Golden State's seven-day positivity rate stands at 10%.

California Gov. Gavin Newsom has ordered regions to follow a stay-at-home order if their intensive care unit capacity falls below 15%.

The San Joaquin Valley and Southern California regions have already met this criteria and are under stay-at-home orders until at least Dec. 28.

The Greater Sacramento region now meets the criteria and a stay-at-home order will go into effect there the night of Dec. 10.

Northern California and the Bay Area are the two remaining regions with ICU capacities above 15%.

Once the FDA approves the Pfizer/BioNTech vaccine, 2.9 million doses will go out immediately in the U.S., said Gen. Gus Perna, commander of the Army Materiel Command. The second batch of 2.9 million will be close behind, within 21 days, Perna said.

Twenty million Americans are expected to be vaccinated by the end of 2020, Health and Human Services Secretary Alex Azar said.

"We remain confident that across our portfolio of multiple vaccines, we will have enough doses for any American who wants a vaccine by the end of the second quarter of 2021," Azar said.

After two allergic reactions to the Pfizer/BioNTechvaccine were reported in the United Kingdom, Moncef Slaoui, Trump’s chief scientific adviser on vaccines, told reporters, "The expectation would be that subjects with known severe reaction, allergic reaction, should not take the vaccine, until we understand exactly what happened here."

ABC News' Anne Flaherty contributed to this report.

The last week marks the deadliest week for the U.S. since the beginning of the pandemic, with 15,578 deaths -- roughly equivalent to 92 deaths reported every hour.

The U.S. is now averaging more than 200,000 new cases each day -- three times higher than the country's summer peak in July, and more than six times higher than the country's spring peak in April.

There has not been a single day with less than 100,000 daily cases for the last five straight weeks, according to an ABC News analysis of data compiled by the COVID Tracking Project.

In the last week alone, the U.S. has reported 1.4 million new COVID-19 cases, more than any other week on record, and equivalent to 1 in every 231 Americans testing positive.

With numerous days now over the 200,000 mark, the seven-day average of new coronavirus cases has increased by 87% in the last month.

ABC News' Arielle Mitropoulos contributed to this report.

Pennsylvania Gov. Tom Wolf said he tested positive for COVID-19 on Tuesday and is isolating at home.

"I have no symptoms and am feeling well," Wolf said in a statement. “I am continuing to serve the commonwealth and performing all of my duties remotely."

Wolf's wife has been tested and is awaiting results.

The chief science adviser to Operation Warp Speed, the U.S. government's initiative to expedite vaccine development, said he doesn't know what vaccine-related executive order President Donald Trump is expected to sign on Tuesday.

"Frankly, I don't know and, frankly, I'm staying out of this. I can't comment," Dr. Moncef Slaoui told ABC News chief anchor George Stephanopoulos in an interview Tuesday on "Good Morning America."

When pressed on the matter, Slaoui added: "Our work is, you know, rolling. We have plans. We feel that we can deliver the vaccines as needed, so I don't exactly [know] what this order is about."

Trump is expected to discuss the order at a COVID-19 vaccine summit to be held at the White House later Tuesday, multiple White House officials told reporters during a background briefing on Monday evening. While it's not entirely clear on how exactly the order would work, the move is designed to prevent the U.S. government from shipping any vaccine doses it has purchased to aid foreign countries until all the needs within the United States are met.

White House officials also denied reports that the Trump administration turned down an offer last summer to purchase an additional 400 million doses of a COVID-19 vaccine developed by U.S. pharmaceutical giant Pfizer and its German partner BioNTech, and that the companies now may not be able to provide more of their vaccine to the United States until June 2021 because they have committed those doses to other countries.

When asked about the matter, Slaoui explained Operation Warp Speed's strategy in securing vaccine doses.

"We selected six different vaccines to build a portfolio to manage the risk that some may work and some may not work, but also to ensure that as more than one would work that we would accumulate vaccine doses from this portfolio of vaccines," he said. "If somebody came to us and said, let's buy more of this vaccine or that vaccine, no one reasonably would buy more from any one of those vaccines because we didn't know which one would work and which one may be better than the other. Once the vaccine's performance becomes known is the right time, given the strategy we've taken, to go and order more vaccine doses, which we may be doing. And frankly, the constructive thing to do if one of the suppliers has challenges producing enough vaccine doses is to roll our sleeves and help ensure that capacity can be increased."

Slaoui said he's confident the U.S. government will be getting vaccines to Americans who need them "as soon as possible" and that plans are "still on track."

"We will work with Pfizer to try and increase capacity and have those vaccines available," he said. "We have two more vaccines from J&J and AstraZeneca that will be completing their Phase 3 trials in January and most likely, I hope, be approved for use in February. We have tens of millions of doses from those vaccines, you know, participating to the volume of vaccines we need to immunize the U.S. population as we promised, all of it by the middle of the year 2021 and that's still on track."

Slaoui said Operation Warp Speed has a meeting with President-elect Joe Biden's transition team scheduled for Thursday.

"We look forward to, you know, sharing all the information and working together," he said. "Our objective has always been outside of politics and making sure we make available these vaccines for the U.S. people, and that's what we're doing."

ABC News' Ben Gittleson, John Parkinson and Eric Strauss contributed to this report.