three million doses are being given on average each day, compared with well under one million when Mr. Biden took office in January, according to the Centers for Disease Control and Prevention. Every state has now given at least one dose to a quarter or more of its population. About 62.4 million people — 19 percent of Americans — have been fully vaccinated.
“Today, we are pleased to announce another acceleration of the vaccine eligibility phases to earlier than anticipated,” Gov. Larry Hogan of Maryland said on Monday, announcing that all Maryland residents 16 or older would be eligible from Tuesday for a vaccine at the state’s mass vaccination sites, and from April 19 at any vaccine provider in the state.
Also on Monday, Gov. Philip D. Murphy of New Jersey said residents 16 or older in his state would be eligible on April 19. Mayor Muriel Bowser of Washington said later on Monday that city residents 16 or older would also be eligible on April 19.
That leaves two states, Oregon and Hawaii, keeping to Mr. Biden’s original deadline of May 1. Their governors did not immediately respond to requests for comment about whether they would broaden eligibility sooner, but Gov. Kate Brown of Oregon announced on Monday that all frontline workers and their families, as well as those 16 or older with underlying health conditions, would be eligible immediately.
In Hawaii, 34 percent of residents have received at least one dose; in Oregon, the figure is 31 percent. Alabama has vaccinated the lowest proportion of its residents, at 25 percent.
But as Ms. Brown noted in her announcement about eligibility — and as experts have warned for weeks — “we’re in a race between vaccines and variants.”
Along with dangerous coronavirus variants that were identified in Britain, South Africa and Brazil, new mutations have continued to pop up in the United States, from California to New York to Oregon.
The shots will eventually win, scientists say, but because each infection gives the coronavirus a chance to evolve further, vaccinations must proceed as fast as possible.
As that race continues, the optimism sown by the steady pace of vaccinations may be threatening to undermine the progress the nation has made. Scientists also fear Americans could let their guard down too soon as warmer weather draws them outside and case levels drop far below the devastating surge this winter.
Cases are now rising sharply in parts of the country, with some states offering a stark reminder that the pandemic is far from over: New cases in Michigan have increased 112 percent and hospitalizations have increased 108 percent over the past two weeks, according to a New York Times database.
The United States is averaging more than 64,000 new cases each day, an 18 percent increase from two weeks earlier. That’s well below the peak of more than 250,000 new cases daily in January, but on par with last summer’s surge after reopenings in some states, like Arizona, where patrons packed into clubs as hospital beds filled up. The United States is averaging more than 800 Covid-19 deaths each day, the lowest level since November.
Yet again, governors across the country have lifted precautions like mask mandates and capacity limits on businesses. Medical experts have warned that these moves are premature, and Mr. Biden has urged governors to reinstate the restrictions.
Travel is up again, too, with more than one million people passing through airport security each day in the United States since March 11, according to the Transportation Security Administration. On Sunday, more than 1.5 million people passed through T.S.A. checkpoints. The C.D.C. said last week that fully vaccinated Americans could travel domestically with low risk, but should still follow precautions like wearing masks.