The 1918 Flu pandemic lasted two winters. That's the best example that we have.
Why is this the best example we have? Simply because the symptoms are "flu like"? On one hand most of teh world did not have access to quality hospital care, there were no respirators, and there was no communication of cases or symptoms across regions or countries. On the other hand we didn't have 5-6MM people flying from place to place every day in 1918.
With that said, in 18 or so months when we have a vaccine I can see a lot of pent up demand.
Again, you are assuming a lot. Maybe we will have an effective vaccine in 18 months, maybe not. Said vaccine could be easy to synthesize and we might be able to roll out several million doses each day. Or it could be finicky as hell and expensive, and we may never have enough to treat teh general public.
We also have zero idea about the long-term efficacy of a future vaccine. For reasons that are largely still unknown, or bodies are very good at prolonged immunity for some strains, but not others.
Some projections suggest 150,000 deaths in the US are possible.
Not to be grim, but I think that with what we are seeing in Italy and Germany that we can safely say that is off by an order of magnitude. Or to be more specific: I'd bet money that we are going to see at least 1 million deaths in the USA, but less than 10 million.
The Resolve to Save Lives ran a number of simulations given what we know (and including the viariance in what we know) - the range of deaths in the US ranged from 327 to 1.6MM. To quote CDC director Tom Frieden:
"anyone who says they know where this is going with confidence doesn't know enough about it"So deaths in the US could be less than a thousand, or it could ultiamtely be more than a million.
I'll end on an upbeat note: the U.S. stock market over the past 12 months has a return of about -3%, including today's losses. For a pandemic, that's not bad!
A good reminder. A drop of 30% from Feb highs (still below where we are today) pushes us all the way back to 2017. An additional 20% from where we are right now ends us equal to June 2016.