By then, several positions will have already been eliminated, leaving fewer jobs to go back to. Several jobs have already been eliminated through layoffs and more are coming.
There have already been reinfections and studies suggesting long term immunity is not achievable. If our body is not capable of the long term immune response to make a vaccine work, there can be no vaccine.
Covid is no more deadly than diseases, like chicken pox and measles, we used to accept as normal. They did not cause us to shut down our lives. Yes, if a vaccine is developed (and that's a pretty big IF) we should take it and the further reduced risk. But it does not justify shutting everything down in the meantime and causing irreparable financial damage to untold numbers.