So now we have some clinical data on yet another category of vaccine: SinoPharm's ([[SHTDF]], [[SHTDY]]) inactivated coronavirus candidate. This is one of the classic vaccine techniques, where an infectious virus is altered by some sort of protein-denaturing treatment (heating or reactive chemistry) to make it noninfectious. But such particles can retain enough of their protein surfaces to set off a useful immune response - the tricky part is inactivating the virus enough so that it can't infect cells and replicate, but not so much that it presents totally different proteins to the immune system