The capsid that covers the harmful part of the flu virus mutates and is why immunity does not transfer from year to year or strain to strain. The capsid is onl

The capsid that covers the harmful part of the flu virus mutates and is why immunity does not transfer from year to year or strain to strain. The capsid is only the outermost part of the viral particle, however. Anything which targets the inner part would be far more effective. Researchers have been working on getting to that part and are finally starting to get close. HIV is a whole different ball of wax from flu, though, and I wouldn't discuss them in the same way.