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...