With some coronavirus vaccine trials in their much-anticipated final stage, U.S. officials and experts are wrestling with one of the most difficult issues facing the country: Who should be first to get limited doses of a vaccine during one of the worst public health crises in a century?

Discussions have begun to identify priority groups for initial vaccination against COVID-19, the disease caused by the virus. Those discussions, involving federal health officials and outside experts, are based on planning developed during the 2009 H1N1 influenza pandemic. Highest priority would go to health-care and essential workers and high-risk populations. This proposed group would also include older adults, residents of long-term-care facilities and people with underlying medical conditions.

A federal advisory panel that provides vaccine recommendations to the Centers for Disease Control and Prevention presented an overview of the priority groups last month and is scheduled to meet again on the issue Wednesday.

As officials and experts race to stop the pandemic, they are grappling with the fraught nature of establishing vaccination priorities. Clinical trials of at least two experimental vaccines have shown encouraging results and this week moved into final-stage testing for safety and effectiveness in 30,000 participants. If a vaccine is shown to be effective, U.S. officials have said the first doses could be available by the end of the year.

The decision-making will take place over the next few months and is certain to be controversial, experts said. Officials and experts must address a host of issues, including how much consideration should be given to race and ethnicity because of the disproportionate impact of COVID-19 on communities of color. Aside from doctors and nurses, will cafeteria workers and cleaning staff at hospitals be considered essential personnel? What about teachers who keep schools running so parents and others can go back to work?

“This is going to be controversial and not everybody’s going to like the answer,” said Francis Collins, director of the National Institutes of Health, referring to the process of establishing priorities. He spoke last week at the kickoff meeting of a committee of experts helping with planning. “There will be many people who feel that they should have been at the top of the list and not everybody can be.”

That committee of experts is developing a framework to help the federal advisory panel and the CDC set final vaccination priorities. The experts are from an independent advisory group, the National Academies of Sciences, Engineering and Medicine, and from the National Academy of Medicine. The panel, which is supposed to have an initial draft ready by the end of August and a final version by the end of September, was formed at the request of the directors of the NIH and the CDC.

The overview of proposed priority groups laid out by the federal advisory panel includes subsets within those that should get the highest consideration. At the top of the list: an estimated 12 million critical health-care and other workers. The first doses would go to a subset described as “highest risk medical, national security, and other essential workers” needed to protect health-care infrastructure and critical societal functions, according to presentations and discussions at the June meeting of the Advisory Committee on Immunization Practices.

But what’s at stake goes beyond allocation of the first shots. The process of identifying priority groups is a chance for health officials and scientists to adjust sometimes-unrealistic expectations about when a vaccine is likely to be available.

It is also an opportunity to reset public trust in government and institutions at a time when “there is a profound sense of people feeling they are not being protected by the people and institutions that are supposed to protect them,” said Monica Schoch-Spana, a medical anthropologist at the Johns Hopkins Center for Health Security. She co-chaired a working group that recently released a report on COVID-19 vaccination.

“We have a socially, politically and racially fragmented society that is under the stress of a disease that causes illness and death. And we’ve seen an uneven – I’m being polite – response to it,” she said. “If there was ever a time when public perception of fairness and justness was important, that would be now.”

Top federal officials also need to make sure the public is hearing a clear and consistent message and show the government is able to keep its promises, Schoch-Spana said. During the 2009 H1N1 pandemic, there were overly optimistic projections of vaccine supply during the second wave of the disease in October, when demand was high. By the time an adequate supply of vaccine arrived, demand had fallen.

In addition to essential workers and those most affected by health disparities, Collins said a priority list should include the military and locations where the virus is most active. He said the committee should consider giving priority to volunteers in vaccine clinical trials who received a placebo instead of a vaccine dose.

“I think probably we owe them as a consequence of their participation in the trial some special priority in terms of access to the vaccine if it’s proven to be successful,” he said.

During last month’s meeting of the CDC’s Advisory Committee on Immunization Practices, committee members discussed whether priority should be given to children and pregnant women. Consideration of race or ethnicity as a criteria for vaccine prioritization drew considerable discussion.

Jose Romero, a pediatric infectious-disease specialist at Arkansas Children’s Hospital Research Institute who chairs the CDC immunization committee, spoke of Black, Latino and Native American communities hit hard by COVID-19. The COVID-19 death toll is twice as high among people of color younger than 65 as for White Americans, according to a recent CDC report.

“If we fail to address this issue of racial and ethnic groups as a high risk in prioritization, whatever comes out of our group will be looked at very suspiciously and with a lot of reservation,” he said.

Another committee member, Sharon Frey, an infectious-disease specialist at Saint Louis University School of Medicine, agreed it was important to include racial and ethnic groups in a high-priority group. Consideration should be given to the urban poor and working poor who often have other underlying medical conditions, live in crowded homes and can’t take off work “because they have to bring money home to feed their families,” Frey said.

When more data about vaccine effectiveness in different groups becomes available, officials and experts may adjust recommendations, according to Nancy Messonnier, director of CDC’s National Center for Immunization and Respiratory Diseases. If the first vaccine that’s available produces less of an immune response in older adults, that could change the priority consideration for older adults, Messonnier said.