> Though, and correct me if I'm wrong, aren't they still extremely less stable than DNA viruses? That's correct. Worse, the proofreader doesn't have to protec

> Though, and correct me if I'm wrong, aren't they still extremely less stable than DNA viruses? That's correct. Worse, the proofreader doesn't have to protect all parts equally... > Which is why only short/medium term immunity is usually possible? No. For some viruses active immunity just doesn't last particularly long for reasons we don't understand (or at least it was described as not understood in every paper I've seen on the subject). For some viruses you can be reinfected months later with exactly the same virus. This is the case for several cold causing viruses.