The CDC’s scientific pronouncement came without policy guidance. It left states, cities, and businesses with four bad options:
The mandate. Keep making everyone mask up. Force vaccinated people to take this unneeded precaution in order to force unvaccinated people to keep protecting themselves, each other, and the immunocompromised.
The honor system. Request (or urge or beg or even “require”) unvaccinated but not vaccinated people to wear masks but don’t monitor or enforce the policy. Some unvaccinated people will inevitably go unmasked. They won’t significantly harm vaccinated people, but they will cause more infections among the unvaccinated and immunocompromised.
The vaccine passport. Find ways to distinguish people who are vaccinated from those who aren’t. Set the former free and require the latter to continue taking precautions, hopefully increasing their incentive to get vaccinated.
Splitting the difference. State and local governments might make masks optional if and when case count and positivity levels get low enough, and require them again if and when those metrics rise again. Stores might alternate “masks required days” and “masks optional days.”