As more and more Americans get vaccinated, many are wondering when they can throw out their masks.

The answer, my colleague Apoorva Mandavilli reports, largely depends on two factors — how quickly Covid rates drop and what percentage of people remain unvaccinated in your community.

Scientists still don’t know if vaccinated people can spread the virus to the unvaccinated. While the vaccines work well in preventing severe illness and death, data is still missing on how well they stop the virus from taking root in an immunized person’s nose, where it could be spread to others.

If some previous vaccines are a guide, then we may have to live with masks for a while longer. Inoculations against the flu, rotavirus, polio and pertussis all prevent severe disease, but not infection.

Virus variants are also changing the calculus, since some vaccines are less effective against some of them — and at least one variant discovered in Brazil may be able to reinfect those who recovered from an earlier version of the virus.

Still, early research suggests the vaccines do cut transmission. Experts say that an 80 percent drop in transmissibility might be enough to allow vaccinated people to ditch masks, especially if most of the population is inoculated. But with stubbornly high infection rates across the country, and with only 26.2 million people fully vaccinated and 51.8 million having received a first shot, experts say that those who are immunized must continue to mask.

And finally, how would a stranger be able to trust that an unmasked person had actually been fully vaccinated? (Especially when mask skepticism appears to still be prevalent in some pockets of society.)