The thing is we may never get a vaccine. It is far from a guarantee and if I had to wager a percentage I would say its more likely we don't get a vaccine, and if we do its not effective or has worst side effects then the actual virus. So we either hope for the virus to mutate into a less contagious and less deadly virus which is definitely possible as viruses are constantly mutating or we develop herd immunity. Or another possible option is develop treatment for the symptoms, a band aid to help people get through the worst symptoms.