With the coronavirus pandemic surging and initial vaccine supplies limited, the United States faces a hard choice: Should the country’s immunization program focus in the early months on the elderly and people with serious medical conditions, who are dying of the virus at the highest rates, or on essential workers, an expansive category encompassing Americans who have borne the greatest risk of infection?

Health care workers and the frailest of the elderly — residents of long-term-care facilities — will almost certainly get the first shots, under guidelines the Centers for Disease Control and Prevention issued on Thursday. But with vaccination expected to start this month, the debate among federal and state health officials about who goes next, and lobbying from outside groups to be included, is growing more urgent.

It’s a question increasingly guided by concerns over the inequities laid bare by the pandemic, from disproportionately high rates of infection and death among poor people and people of color to disparate access to testing, child care and technology for online schooling.

“It’s damnable that we are even being placed in this position that we have to make these choices,” said the Rev. William J. Barber II, a co-chairman of the Poor People’s Campaign, a national coalition that calls attention to the challenges of the working poor. “But if we have to make the choice, we cannot once again leave poor and low-wealth essential workers to be last.”

Ultimately, the choice comes down to whether preventing death or curbing the spread of the virus and returning to some semblance of normalcy is the highest priority. “If your goal is to maximize the preservation of human life, then you would bias the vaccine toward older Americans,” Dr. Scott Gottlieb, the former Food and Drug Administration commissioner, said recently. “If your goal is to reduce the rate of infection, then you would prioritize essential workers. So it depends what impact you’re trying to achieve.”

The trade-off between the two is muddied by the fact that the definition of “essential workers” used by the C.D.C. comprises nearly 70 percent of the American work force, sweeping in not just grocery store clerks and emergency responders, but tugboat operators, exterminators and nuclear energy workers. Some labor economists and public health officials consider the category overbroad and say it should be narrowed to only those who interact in person with the public.

An independent committee of medical experts that advises the C.D.C. on immunization practices will soon vote on whom to recommend for the second phase of vaccination — “Phase 1b.” In a meeting last month, all voting members of the committee indicated support for putting essential workers ahead of people 65 and older and those with high-risk health conditions.

Historically, the committee relied on scientific evidence to inform its decisions. But now the members are weighing social justice concerns as well, noted Lisa A. Prosser, a professor of health policy and decision sciences at the University of Michigan.

“To me the issue of ethics is very significant, very important for this country,” Dr. Peter Szilagyi, a committee member and a pediatrics professor at the University of California, Los Angeles, said at the time, “and clearly favors the essential worker group because of the high proportion of minority, low-income and low-education workers among essential workers.”

That position runs counter to frameworks proposed by the World Health Organization, the National Academies of Sciences, Engineering, and Medicine, and many countries, which say that reducing deaths should be the unequivocal priority and that older and sicker people should thus go before the workers, a view shared by many in public health and medicine.

Dr. Robert Redfield, the C.D.C. director and the nation’s top public health official, reminded the advisory committee of the importance of older people, saying in a statement on Thursday that he looked forward to “future recommendations that, based on vaccine availability, demonstrate that we as a nation also prioritize the elderly.”

Once the committee votes, Dr. Redfield will decide whether to accept its recommendations as the official guidance of the agency. Only rarely does a C.D.C. director reject a recommendation from the committee, whose 14 members are selected by the Health and Human Services secretary, serve four-and-a-half-year terms and have never confronted a task as high in profile as this one.

But ultimately, the decision will be up to governors and state and local health officials. They are not required to follow C.D.C. guidelines, though historically they have done so.

Defining ‘essential’

There are about 90 million essential workers nationwide, as defined by a division of the Department of Homeland Security that compiled a roster of jobs that help maintain critical infrastructure during a pandemic. That list is long, and because there won’t be enough doses to reach everyone at first, states are preparing to make tough decisions: Louisiana’s preliminary plan, for example, puts prison guards and food processing workers ahead of teachers and grocery employees. Nevada’s prioritizes education and public transit workers over those in retail and food processing.

At this early point, many state plans put at least some people who are older and live independently, or people who have medical conditions, ahead of most essential workers, though that could change after the C.D.C. committee makes a formal recommendation on the next phase.

One occupation whose priority is being hotly debated is teaching. The C.D.C. includes educators as essential workers. But not everyone agrees with that designation.

Marc Lipsitch, an infectious-disease epidemiologist at Harvard’s T.H. Chan School of Public Health, argued that teachers should not be included as essential workers, if a central goal of the committee is to reduce health inequities.

“Teachers have middle-class salaries, are very often white, and they have college degrees,” he said. “Of course they should be treated better, but they are not among the most mistreated of workers.”

Elise Gould, a senior economist at the Economic Policy Institute, disagreed. Teachers not only ensure that children don’t fall further behind in their education, she said, but are also critical to the work force at large.

“When you talk about disproportionate impact and you’re concerned about people getting back into the labor force, many are mothers, and they will have a harder time if their children don’t have a reliable place to go,” she said. “And if you think generally about people who have jobs where they can’t telework, they are disproportionately Black and brown. They’ll have more of a challenge when child care is an issue.”

In September, academic researchers analyzed the Department of Homeland Security’s list of essential workers and found that it broadly mirrored the demographics of the American labor force. The researchers proposed a narrower, more vulnerable category — “frontline workers,” such as food deliverers, cashiers and emergency medical technicians, who must work face to face with others and are thus at greater risk of contracting the virus.

By this definition, said Francine D. Blau, a labor economist at Cornell University and an author of the study, teachers belong in the larger category of essential workers. However, when they work in classrooms rather than remotely, she said, would they fit into the “frontline” group. Individual states categorize teachers differently.

Dr. Blau said that if supplies are short, frontline workers should be emphasized. “These are a subset of essential workers who, given the nature of their jobs, must provide their labor in person. Prioritizing them makes sense given the heightened risk that they face.”

The analysis, a working paper for the National Bureau of Economic Research, is in line with other critics, who say that the list of essential workers is too wide-ranging.

“If groups are too large, then you’re not really focusing on priorities,” said Saad B. Omer, director of the Yale Institute for Global Health, who worked on the vaccination frameworks for the W.H.O. and the National Academies.

The essential workers on the federal list make up nearly 70 percent of the American labor force, the researchers said, compared with 42 percent for the frontline workers. Women made up 39 percent of frontline workers and, in certain occupations, far more. Frontline workers’ education levels are lower, as are their wages — on average, just under $22 an hour. The proportion of Black and Hispanic workers is higher than in the broader category of essential workers.

Death vs. transmission

Some health policy experts said that to prioritize preventing deaths rather than reducing virus transmission was simply a pragmatic choice, because there won’t be enough vaccine initially available to make a meaningful dent in contagion. A more effective use of limited quantities, they say, is to save the lives of the most frail.

Moreover, vaccine trial results so far show only that the shots can protect the individuals who receive them. The trials have not yet demonstrated that a vaccinated person would not infect others. Though scientists believe that is likely to be the case, it has yet to be proved.

Harald Schmidt, an expert in ethics and health policy at the University of Pennsylvania, said that it is reasonable to put essential workers ahead of older adults, given their risks, and that they are disproportionately minorities. “Older populations are whiter, ” Dr. Schmidt said. “Society is structured in a way that enables them to live longer. Instead of giving additional health benefits to those who already had more of them, we can start to level the playing field a bit.”

But to protect older people more at risk, he called on the C.D.C. committee to also integrate the agency’s own “social vulnerability index.”

The index includes 15 measures derived from the census, such as overcrowded housing, lack of vehicle access and poverty, to determine how urgently a community needs health support, with the goal of reducing inequities.

In a new analysis of the states’ preliminary vaccine plans, Dr. Schmidt found that at least 18 states intended to apply the index. Tennessee, for one, has indicated that it will reserve some of its early allotments for disadvantaged communities.

Still, some people believe it is wrong to give racial and socioeconomic equity more weight than who is most likely to die.

“They need to have bombproof, fact-based, public-health-based reasons for why one group goes ahead of another,” said Chuck Ludlam, a former Senate aide and biotech industry lobbyist who protested putting essential workers ahead of older people in comments to the committee. “They have provided no explanation here that will withstand public scrutiny.”

Blurred lines, many unknowns

Further complicating matters, the different priority groups discussed by the C.D.C. committee are overlapping — many essential workers have high-risk conditions, and some are older than 65. Some states have suggested that they will prioritize only essential workers who come face to face with the public, while others have not prioritized them at all.

Even some people whose allegiance lies with one group have made the case that others should have an earlier claim on the vaccine. Marc Perrone, president of the United Food and Commercial Workers Union, which represents 1.3 million grocery and food processing workers, said that despite the high rate of infection among his members, he thought that older adults should go first.

“Here’s the thing: Everybody’s got a grandmother or grandfather,” Mr. Perrone said. “And I do believe almost everybody in this country would want to protect them, or their aging parents.”

But Dr. Nirav Shah, Maine’s top public health official, said he respectfully disagreed, repeating the explanation he had given his in-laws — who are older but in good health and able to socially distance.

He said: “I’ve told them: ‘You know what? I’m sorry, but there are others that I need to get this vaccine to first, so that when you guys get vaccinated, the world you come back into is ready to receive you.’”

All these plans are, of course, unfurling with essential information still unknown.Many state officials said that as on-the-ground realities emerge, they fully expect their plans to evolve.

One uncertainty: given the high rates of apprehension swirling around this vaccine, how many people in the early groups will actually line up for it?

“If a high proportion of essential workers decline to get the vaccine, states will have to quickly move onto the next group anyway,” said Dr. Prosser, the University of Michigan health analyst. “Because once the vaccines arrive, they will have to be used in a certain amount of time before they degrade.”

Additional work by Jugal K. Patel.