If you're concerned about the long term effects of the vaccine, you should be double concerned about the long term effects of the much more complex and much less understood virus.
Not necessarily, there have been reports of people being infected via central air units in large building (apartments, condos, etc.).
Albeit, I do not believe it is that common, it's still possible. However, if you isolated in a remote location in the woods miles away from humanity, then perhaps you'd be safe, I suppose.
It’s pretty uncommon for multi tenant dwellings to share a common air ducting system, at least in newer buildings. I live in an apartment and my “across the hall” neighbors did get COVID, no issues for me.
