Okay, well I poked around and I can't find a link to the study I was thinking of. Maybe I saw it somewhere other than facebook, but I did find this YouTube video doing an analysis on the cross-reactivity of antibodies for other viruses being cross-reactive with SARS-CoV2. Kevin McKernan is a genomics expert who worked on the human genome project back in the '90s and early '00s. He goes over a lot of the theory behind why many don't get sick when exposed to Covid-19. https://www.youtube.com/watch?reload=9&v=2SfXZa7-JKM&feature=youtu.be&fbclid=IwAR0uce2be0mt4pjp1nLt-2q_2omt7shNiI6wjZkcKJ1qW8Ho34SGNW0kmeE