My concern with a vaccine is how it functions. If it's like a conventional vaccine (weakened virus that stimulates immunity but doesn't cause illness) then it might be easy to require it by law in some circumstances, e.g. attend public school. But if it takes a novel approach and its long-term safety is not yet known, anti-vaxxers will have a solid case for refusing it.
There are 154 vaccines in development, conventional and otherwise. Many will work, probably including some conventional.