I have a few patients in my practice with double c

I have a few patients in my practice with double contraction of this virus as well as two healthcare providers. My knowledge of Virology is no where near a few others on this board and would appreciate some explanation form MDV on this topic. How can we ever have an effective vaccine for Covid when we see these cases of double contractions happening all the time?
Hence why i think we are going to have to deal with this for a very long time and Leron will be the ultimate life saver. IMHO of course.