My small non-profit elected to do the same. Just prior, they rolled out extra vacation time for the vaccinated if they would allow HR to get a photocopy of their vax card and keep it on file -- so they have a pretty good idea as to who is and who isn't.

Unvaccinated people will be required to wear masks at all times and will not be able to use some of the common areas, like the gym. Enforcement of masks was tight where I am and has since escalated. Snitch culture is rampant.

It's kind of incredible -- what was once a relatively decent place to work is now utterly miserable.