At least four candidates are near the finish line in the U.S. coronavirus vaccine race. A key point to note, however, is that the vaccine isn't an end-all solution to the pandemic. That's in large part because any inoculations developed now are focused on simply preventing symptoms from arising, rather than blocking out the virus altogether. The latter goal is a secondary endpoint, according to Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. "The primary thing you want to do is that if people get infected, prevent them from getting sick, and if you prevent them from getting sick, you will ultimately prevent them from getting seriously ill," Fauci said. "What I would settle for, and all of my colleagues would settle for, is the primary endpoint to prevent clinically recognizable disease," he said. That level of protection would be the ultimate goal to diffusing the crisis, but is hard to do with companies facing an immediate demand for some sort of solution. While no vaccine is 100% effective, having a majority of the population inoculated and higher percentages of efficacy is the best to hope for. The U.K. is looking at challenge trials, which intentionally infect a smaller group of participants with the virus in an effort to test a vaccine's or treatment's efficacy. Fauci said the U.S. is not anticipating such a move because the rate of spread is so high in the country that it's sufficient enough of an environment to test the vaccine.