Not this specific one; but the Spanish flu was pretty bad and they never developed a vaccine for that one. And, right-wingers were purposefully being rebels without a Cause with their anti-mask and anti-vax stances.
I disagree.
Spanish flu still comes back every decade or so.
Then why is it millions are not dying from it whenever it does come back, even though no one ever did a vaccine for it?
The answer is that Spanish flu NEVER was very serious.
The reason so many died is NOT that it was so lethal or infectious.
The reason so many died is that is lasted so long, (over 2 years, 20 times the normal flu duration).
And the reason it lasted so long, (over 2 years), is that we went with masks and social distancing.
Masks and social distancing prevents herd immunity.
Herd immunity is when an epidemic gets too greedy, infects the easy local hosts too quickly, and then dies out because it runs out of easy local hosts.
So to end any epidemic quickly, then the goal should be to deliberately accelerate infection of easy local hosts, to use them up.
Then it is over quickly.
The only time you do not want to do this is if the epidemic is too lethal.
But then you do not just wear masks and social distance, but do full quarantine with contact tracing.
Never do social distancing and masks unless you are going for full quarantine.
If you are not doing full quarantine, then the method is herd immunity, and masks and social distancing are at cross purposes to herd immunity.
With herd immunity you don't want to conserve easy local hosts behind masks and social distancing.
You want to use them up instead, so they have recovery immunity and can't host the virus.