Pressure is mounting to find a vaccine for COVID-19 as the U.S. death toll from the virus officially passed 100,000. Right now, there are now roughly 100 candidates for a vaccine in the works with a few fast-tracked for human trials. Vaccine development has multiple stages that usually take years to ensure the treatment is safe and effective. Special contributor Joie Chen gives us a look at the push being made for a different and controversial type of testing – human challenge trials.


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