[jyl]

There are a number of vaccines for other diseases that require a sequence of multiple doses.

It may be that these particular vaccines work best with two doses several months apart, instead of two doses 20 days apart. There hasn’t been time to test all the different dosing schedules and figure out what is ideal. It is clear that the two initial doses in quick succession provide very good protection (in most people) for around six months, at which time, for best protection, a third shot (booster) is needed, and that booster raises neutralizing antibody levels by (if memory serves) around 40X.

We don’t yet know if this will end up being an annual shot, or if the three dose regime is all that is needed.

We also don’t know how much the Omicron variant reduces the vaccines’ protection, but it is likely that it does reduce it to some extent, hence all the more reason to get boosters.

It would be nice if we knew all this stuff, but we don’t yet. If you want to wait until everything is fully known, then you’ll have to wait for years. Best to take sensible steps in the meantime.