DENVER — In research laboratories around the world, the race to find a COVID-19 vaccine is on. Already, more than 30,000 volunteers have agreed to participate in Phase 3 vaccine trials in the U.S., according to officials from the U.S. Department of Health and Human Services.China, meanwhile, has been giving an experimental vaccine to medical professionals, border inspectors and other workers in high-risk professions, according to CNN.President Trump has committed the U.S. to approving a vaccine by the end of the year.Once a vaccine is approved, however, should cities, states or businesses mandate it? Denver7 heard multiple perspectives on...