For the first you can just Google for "hiv rapid mutation", example: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5414815/ https://www.ncbi.nlm.nih.gov/pmc/arti

For the first you can just Google for "hiv rapid mutation", example: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5414815/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5414815/. The OP article contains a lot of details too. For the second see something like "covid spike sequence modification", for example this seems like an accessible article: https://cen.acs.org/pharmaceuticals/vaccines/tiny-tweak-behind-COVID-19/98/i38 https://cen.acs.org/pharmaceuticals/vaccines/tiny-tweak-behi... It was all thanks to the research on previous coronaviruses, MERS specifically. The Pfizer/Moderna vaccines have just copied it (of course that simple modification is not all it took, but that was definitely required for success).