I would like to know whether anyone has experimented with drugs that conjugate an antibody that is specific to a deadly pathogen, with an antigen found on the surface of a milder pathogen from the same family. When administered to a victim of the serious infection, such a drug would coat the surface of the deadly bug and fool the immune system into thinking it is the milder one. How could that help? Suppose that the mild bug is one already familiar to nearly everyone's immune system. That could be either because it is a common infection, or because nearly everyone has been vaccinated against it using a vaccine that includes that particular antigen. Either way, it would mean that the immune system is already primed to respond to the milder bug, so its response might be stronger, more rapid, and more specific than it is able to mount in short order against an invader it has never seen before. Provided that the two bugs are similar, the way that the immune system attacks the mild bug could also be effective against the more deadly one.