By| July 31, 2020 -- 13:45 GMT (06:45 PDT)| Topic:There are currently 25 vaccines to fight COVID-19 , another 139 vaccines in a pre-clinical stage, and many more being researched.  But many of those vaccines, if they are at all successful, might not produce an immune response in portions of the population. That's because some people's bodies will react differently to the materials in the vaccine that are supposed to stimulate virus-fighting T cells.  And so just figuring out how much coverage a vaccine has, meaning, how many people it will stimulate to mount an immune response, is a big... READ MORE