People who have been fully vaccinated against COVID-19 and don’t have any symptoms don’t have to quarantine if they’re exposed to someone with the disease, the Centers for Disease Control and Prevention said in new guidelines released today. They should still follow other public health guidelines, like wearing a mask.

Someone is considered fully vaccinated if it has been more than two weeks since they’ve received the second dose of a two-dose vaccine or a dose of a single-dose vaccine.

Even the best vaccines aren’t perfect protection against COVID-19. The Moderna and Pfizer/BioNTech vaccines, the two authorized in the United States so far, are around 95 percent effective at protecting from symptomatic disease. That means there may be a small number of people who are vaccinated who could still get sick. The CDC says people who don’t quarantine should still watch out for symptoms and get tested if they experience any.

Researchers still don’t know how long protection from the vaccines lasts. So for now, the CDC says people should only skip quarantine during the three months after their last dose. That’s the length of time pharmaceutical companies tracked people enrolled in their clinical trials. That could change as companies have more time to gather and analyze data.

The guidelines are similar to those for people who have already been sick with COVID-19 and presumably have some level of natural immunity. If someone is within three months of their initial infection, they also don’t have to quarantine unless they develop symptoms.

Scientists still aren’t sure if people who get vaccinated can spread the coronavirus to others. Research is ongoing, and there should be clearer answers soon. However, based on what we know about vaccines and viral infections, there’s a good chance someone who has been vaccinated would be less contagious if they have an asymptomatic infection. For the CDC, the benefits of minimizing quarantines outweigh the potential, likely small risk of viral spread.

Over 33 million people in the US have received at least one dose of a COVID-19 vaccine.