The highly contagious UK COVID-19 variant first discovered in Kent has now been reported in every state in the US.
More than 15,000 cases of the B117 strain have now been confirmed and experts are concerned variants are behind a surge in infections in many states.
"America appears to be done with the pandemic," Dr Michael Osterholm, director for the Center for Infectious Disease Research and Policy at the University of Minnesota told reporters.
"The virus is not done with us."
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The US has administered 167,187,795 doses of COVID-19 as of Monday morning and distributed 207,891,395 doses, the Centers for Disease Control and Prevention (CDC) said.
Official figures stated the country carried out four million jabs on Saturday alone.
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New Yorkers over the age of 16 can now sign up for coronavirus vaccinations - a major expansion of eligibility.
Teens aged 16 and 17 will be limited to receiving the Pfizer/BioNTech vaccine, since that is the only one that has been authorised for use by people under 18.
Parental consent will be required with certain exceptions including for those who are married or are parents.
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None of the available vaccines have yet been approved for people under 16.
About one in five New York state residents are now fully vaccinated, according to the CDC.
California has announced it will allow professional sports and other indoor events to resume from 15 April.
Venues will be able to have live audiences with strict capacity limits.
Larger private gatherings indoors will be allowed too.
More people will be allowed inside if they show proof of vaccination or a recent negative coronavirus test.
Image:Joe Biden says he hopes families will be able to return to their usual Easter traditions next year
Image:Joe Biden says he hopes families will be able to return to their usual Easter traditions next year
However, the pandemic forced the White House to scrap its traditional Easter Egg Roll for a second straight year.
The president and first lady Jill Biden appeared on the White House balcony along with a mask-wearing Easter Bunny.
In brief remarks, Joe Biden said the virus had forced many Americans to forgo "familiar comforts of the season" but said he hoped the country would be able to return to some of those traditions next year.
Meanwhile, the CDC has also changed its recommendations on daily disinfection of schools.
It updated its guidance on Monday, saying disinfecting chemicals like ammonia and bleach need be used only within 24 hours after an infected person has been there.
Last summer, the agency recommended strong disinfecting chemicals be used daily to prevent the spread of the virus in classrooms.
The updated guidance applies to homes, schools, and other settings that are not hospitals or healthcare facilities.
Image:US Secretary of State Antony Blinken announces his appointment of Gayle Smith to lead US COVID-19 vaccine diplomacy globally
Image:US Secretary of State Antony Blinken announces his appointment of Gayle Smith to lead US COVID-19 vaccine diplomacy globally
On Monday Mr Biden's administration named a coordinator to lead US COVID-19 vaccine diplomacy globally.
Gayle Smith, a former US Agency for International Development (USAID) coordinator under the Obama administration, will now head up Global COVID Response & Health Security at the State Department.
Washington insists it has begun exploring how to share more with other countries.
"I know that many countries are asking the United States to do more, some with growing desperation, because of the scope and the scale of their COVID emergencies," US Secretary of State Antony Blinken said.
"We hear you, and I promise we're moving as fast as possible."
