> We can see with SARS and MERS that a more deadly form may actually reduce overall mortality, since the virus can't spread as effectively. However, we haven't

> We can see with SARS and MERS that a more deadly form may actually reduce overall mortality, since the virus can't spread as effectively. However, we haven't had this effect so far. As GP pointed out, when the unvaccinated are at risk and vaccinated ones are carriers, the dynamics don't remain the same as in the case of Ebola / Nipah / MERS / J. Encephalitis, because the infection retains its virulence while evolutionary pressure selects for a fatal variant, a deadly combination.