@TheDailyCarbuncle we don't have immunity to bubonic plague either.
But we do have antibiotics now which, if they are administered quickly enough, will prevent you dying.
In the past, the best we could do was to isolate when plague came to a village or city. Now we have medical interventions.
With flu, we now have a vaccine. But even that can go wrong - look at swine flu. That crept up and there was no vaccine for a while.
So this will continue until we get either a treatment, immunity in some people that breaks the chain or a vaccine against it. That's the way of a new disease (or a centuries old one in the case of plague). But plague, which killed 40-60% of populations at it's height, even without immunity for anyone, still didn't kill everyone. Otherwise you and I wouldn't be here. Why was that? Why did some people get it and survive? Why did some people not get it at all?
it'll be the same with this. Some won't get it, some will get it more than once, some will die, some will survive with or without immunity. All you can do is try and that's all the medical people can do. The alternative is to either carry on and take your chance or curl up in a corner.