COVID-19 vaccine candidates: 6 front-runners

While the race to develop a COVID-19 vaccine is well underway with over 40 hopeful candidates, only three have entered “Phase I” of clinical trials, the first of three stages of human testing before drug approval. Phase I testing is only a test to see if the vaccine is safe. Researchers won't know if it's effective until Phase II is studied. Below is a brief overview of these three candidates, plus three promising ones that are still in earlier stages of development.abcNews