Only if you consider hanging out with someone a vaccine.

As I mentioned in my reply to you it will be impossible to stop this strain from being deliberately spread by people on their own.

Wouldn't the same social distancing measures that keep the dangerous strain at bay keep the "good" one from spreading? And vice versa.

Yes they would, but if people know their friends have the mild version they might choose to break the social distancing rules and go and visit them for a tea and nice close chat.