The vaccine requirements drew praise from doctors and scientists who have for months stressed the urgency of increasing vaccination rates to contain the spread of the highly contagious Delta variant, which has raised the national caseload to heights last seen in January, overwhelmed hospitals in hard-hit areas and contributed to the deaths, on average, of more than 1,575 people a day.
However, the nation is so deeply polarized politically that even experts seemed split on how effective Mr. Biden’s plan would be.
Dr. Georges C. Benjamin, executive director of the American Public Health Association, said the actions might be “too little, too late,” and warned that Americans opposed to vaccination might dig in and bristle at being told what to do. The American Hospital Association was cautious, warning of the possibility of “exacerbating the severe work force shortage problems that currently exist.”
But Dr. William Schaffner, an infectious disease expert at Vanderbilt University, likened the vaccination requirements to military service in a time of war.
“To date, we have relied on a volunteer army,” Dr. Schaffner said. “But particularly with the Delta variant, the enemy has been reinforced, and now a volunteer army is not sufficient. We need to institute a draft.”
The unvaccinated, though, are not a monolith. They include people who were opposed to vaccines even before the coronavirus pandemic, a group that consumes misinformation on the internet falsely claiming that vaccines commonly cause dangerous side effects and injuries. There are also unvaccinated Americans who have little access to health care, who have not seen a doctor in years and are disconnected from the medical establishment — or who are simply afraid of needles.
Some have religious objections, or are concerned that the vaccines were developed too quickly, though they are the culmination of decades of scientific research. Others have already had Covid and believe that they have immunity that makes a vaccine unnecessary, although the C.D.C. urges previously infected people to get vaccinated because natural immunity may not be enough to prevent reinfection. And millions of unvaccinated Americans have no choice in the matter: They are under 12 years old and are still waiting for a vaccine to be cleared for their use.