Denver will no longer require masks in schools beginning Feb. 26, city officials said, citing "rapidly decreasing" cases and a high vaccination rate.

"It is safe to lift the school mask mandate at this time,” Denver’s chief medical officer, Dr. Sterling McLaren, said in a statement. “The best way to protect children is to make sure they stay up to date with their vaccinations and ensure that the adults around them are vaccinated as well.”

Denver is not alone in ending school mask requirements. School mask mandates in Connecticut and Massachusetts will expire on Feb. 28, followed by New Jersey on March 7, and Oregon and Delaware on March 31.

New York Gov. Kathy Hochul is lifting the statewide requirement to wear a mask indoors or provide businesses with proof of full vaccination.

The indoor mask mandate is set to expire Thursday and will not be renewed, Hochul said.

Hochul said omicron cases peaked Jan. 7 and have dropped 93% since.

The governor said indoor mask requirements would now be left to cities, towns and businesses across the state.

Hochul declined to lift the state’s school mask requirement, citing the vaccination rate among kids 5 to 11.

“We have a little more work to do with the younger kids,” Hochul said. “I think we can do better.”

New York City will maintain its citywide mandates that require proof of vaccination to enter restaurants, theaters and arenas, a spokesperson for the mayor said. Masks continue to be required on mass transit and in schools.

-ABC News' Aaron Katersky

Massachusetts is lifting its statewide school mask mandate effective Feb. 28, Gov. Charlie Baker announced Wednesday.

“Everyone now has the tools and the knowledge to stay safe,” Baker said, citing availability of vaccines, distribution of tests and the relative lack of serious illness among kids. “It’s time to give our kids a sense of normalcy.”

Baker said the state fully supports an individual’s decision to continue to wear a mask and he asked school districts to do the same, echoing New Jersey Gov. Phil Murphy, who told school districts to crack down on any bullying that results from continued mask wearing.

Baker said Massachusetts ranks 2nd in the nation for the highest number of vaccinated kids.

-ABC News' Aaron Katersky

British Prime Minister Boris Johnson announced Wednesday his plans to lift all remaining pandemic-related restrictions in England in less than two weeks.

Addressing lawmakers in the United Kingdom's House of Commons, Johnson said he hopes to scrap England's COVID-19 restrictions as soon as Parliament returns from its upcoming recess on Feb. 21.

"I can tell the House today that it is my intention to return on the first day after the half-term recess to present our strategy for living with COVID," Johnson told lawmakers. "Provided the current encouraging trends in the data continue, it is my expectation that we will be able to end the last domestic restrictions, including the legal requirement to self-isolate if you test positive, a full month early."

Johnson first announced his plans to end all of the so-called Plan B measures last month, starting with mask mandates. He told lawmakers at the time that the legal requirement for people with COVID-19 to self-isolate would be allowed to expire when the regulations lapsed on March 24, but that the date could be brought forward.

Although Johnson is the U.K. prime minister, his government is only responsible for COVID-19 restrictions in England because public health legislation is devolved to national governments within the U.K., meaning that Scotland, Wales and Northern Ireland are responsible for their own pandemic-related policies.

Pfizer said it has postponed its application to the FDA to expand the use of its COVID-19 vaccine for kids under 5.

Pfizer instead will continue with its study on the three-dose vaccine and seek authorization when that data is available.

"We believe additional information regarding the ongoing evaluation of a third dose should be considered as part of our decision-making for potential authorization," Pfizer said.

Dr. Peter Marks, the FDA’s vaccine chief, told reporters Friday, “We realized now, in data that came in very rapidly because of the large number of cases of omicron, that at this time, it makes sense for us to wait until we have the data from the evaluation of a third dose before taking action."

Marks acknowledged that the change was “late breaking” -- the FDA’s committee of independent advisers was scheduled to review and vote on authorizing the vaccine next week -- but said the job of the FDA was to “adjust” to new data amid an unpredictable virus.

“The data that we saw made us realize that we needed to see data from a third dose as in the ongoing trial in order to make the term determination that we could proceed with doing an authorization,” Marks said.

Pfizer has predicted it will be able to submit data on the third dose in early April.

-ABC News' Eric M. Strauss, Cheyenne Haslett