In June, the direction of National Institute of Health, said that, we will need atleast 30000 volunteers to test each vaccine. There are hundreds of vaccines being researched and some of them are under trial. The issue occurs when participants come to know that half the participants will get the real vaccine in the trial and half will get the placebo. This is when most participants drop out as they too want to real vaccine instead of the placebo. But in good news, 138,600 have signed up for a new vaccine trial.