Coronavirus updates: 84% of California population to go on lockdown Sunday night

The first vaccine doses have arrived in the United Kingdom after being transported on freezer trucks from the production facility in Belgium, British authorities confirmed to ABC News. The doses are on their way to distribution centers, which will then dole them out to be administered according to the priority list.

The U.K. Department of Health and Social Care announced Wednesday that a vaccine developed by Pfizer and BioNTech has been approved for use in the U.K.

Vaccinations for some high-priority people could begin next week. The majority of U.K. vaccinations will take place next year.

-ABC News' Angus Hines

California Gov. Gavin Newsom said he's "pulling the emergency break" and asking residents to not gather with people outside of their household.

In regions where the ICU capacity is below 15%, a stay-at-home order will go into effect for three weeks, Newsom said.

ABC Los Angeles station KABC reports that latest projections show all of the state's regions except the Bay Area falling below 15% in the next few days.

In those regions, bars, hair salons and personal care services will close, he said.

"If we don't act now our hospital system will be overwhelmed... we'll continue to see a death rate climb," Newsom said.

Facebook said it will remove false claims about COVID-19 vaccines on Facebook and Instagram.

"This could include false claims about the safety, efficacy, ingredients or side effects of the vaccines. For example, we will remove false claims that COVID-19 vaccines contain microchips, or anything else that isn’t on the official vaccine ingredient list," Facebook said in a statement. "We will also remove conspiracy theories about COVID-19 vaccines that we know today are false."

Dr. Anthony Fauci told MSNBC Americans should expect some protection after getting the first vaccine shot, but in general, they'll be "good" about 7 to 10 days after receiving the second dose.

For Pfizer's vaccine, the doses are given three weeks apart, according to Business Insider.

Regarding children and the vaccine, the director of the National Institute of Allergy and Infectious Diseases predicted trials could start in January with older children before moving on to trials on younger children. Because the vaccine will have been shown to be safe in adults, the trials for children can be relatively smaller and can move faster, he said.

“If we start in January, a couple to three months after that” we could have a vaccine for older children, Fauci said. Then additional trials would need to be done on younger children, he said.

-ABC News' Anne Flaherty