More U.S. states move to expand vaccine eligibility to all adults.

Alabama will allow everyone ages 16 or older to sign up for a Covid-19 vaccine on Monday, joining more than 40 states that have already broadened access in an effort to make all adults eligible by the end of the month.

“This vaccine is our ticket back to normal life,” Gov. Kay Ivey, a Republican, said in a statement on her website. “We are so close to getting Covid-19 in the rearview, and until then, we should all keep wearing our masks, get vaccinated and use the common sense the good Lord gave us.”

While states are moving to vaccinate people faster, they are also easing restrictions aimed at curbing the spread of the coronavirus as Americans tire of the constraints more than a year into the pandemic.

On Friday, the Centers for Disease Control and Prevention announced that about 101.8 million people — nearly one-third of the total U.S. population — had received at least one dose of a Covid-19 vaccine. Yet cases are increasing significantly in many states as new variants of the coronavirus spread through the country, and new deaths on average have only just dipped below 900 a day.

Health officials say that new infections are still at a level that is too high. Earlier this week, Dr. Rochelle Walensky, the C.D.C. director, said that the recent case increases had left her with a recurring sense of “impending doom.”

And although the agency said Friday that fully vaccinated Americans could start traveling — not that they should, only that they could — scientists are not yet certain whether, or how often, vaccinated people may become infected, even briefly, and transmit the virus to others.

Travel has already been increasing nationwide, as the weather warms and people grow tired of pandemic restrictions. Last Sunday was the busiest day at domestic airports since the pandemic began. According to the Transportation Security Administration, nearly 1.6 million people passed through the security checkpoints at American airports.

President Biden warned on Friday that the virus was still not under control and said that measures like mask wearing needed to stay in place.

“I ask, I plead with you, don’t give up the progress we have all fought so hard to achieve,” Mr. Biden said at the White House.

Alabama’s current set of restrictions, including a requirement to wear masks in public, expires on April 9, adding tension to a continuing battle between governors anxious to get their states open again, and the C.D.C. and Biden administration who continue to ask for patience. Several states have already dropped mask mandates.

“Please, this is not politics — reinstate the mandate,” Mr. Biden said Monday about the easing of restrictions nationwide, adding, “The failure to take this virus seriously is precisely what got us into this mess in the first place.”

Almost three million people are being vaccinated across the country per day, according to the seven-day average released by the C.D.C. on Friday. But only about 25 percent of Alabama’s total population has received one shot of a vaccine, below the national average of 31 percent, according to the agency.

Alabama, Georgia and Mississippi are tied as the states with the smallest percentage of people who have received at least one shot.

Isabella Grullón Paz contributed reporting.