NIH Director Francis Collins says several vaccines will probably be needed, use different ones in different areas. This is an acknowledgment that the virus is mutating and one vaccine probably won't be effective on all forms. That's why MRNA's vaccine is going to be harder to develop, but is more promising in the long run -- they're trying to make a vaccine based on the part of the virus that does NOT mutate. Or maybe it will be Imperial College-London's vaccine that works -- they are doing something similar to MRNA's technique.

https://www.bloomberg.com/news/articles/2020-...e-vaccines