The World Health Organization (WHO) has been urging people to continue wearing a facemask and social distancing even if they have been fully vaccinated against COVID-19, according to Scientific American.

The global health agency said fully vaccinated people must continue wearing a mask amid the spread of a new variant and a high level of community transmission in many places.

The currently available COVID-19 vaccines are thought to largely protect against all known variants of the coronavirus, but none is 100% effective.

The WHO has also been recommending fully vaccinated people to keep taking precautions, such as avoiding crowded places and staying in well-ventilated areas.

Dr. Mariângela Simão, WHO Assistant Director-General for Drug Access, Vaccines and Pharmaceuticals, said, “This still continues to be extremely important, even if you are vaccinated, when you have a community transmission ongoing.”

Dr. Bruce Aylward, Senior Advisor to the WHO Director-General, said, “What we’re saying is once you’ve been fully vaccinated, continue to play it safe because you could end up as part of a transmission chain.”

However, the U.S. Centers for Disease Control and Prevention (CDC) has not changed its latest recommendation, stating that people who are fully vaccinated do not need to wear a facemask in indoor or outdoor settings, apart from places that require one, such as hospitals, medical centers, jails, and public transportation.

A CDC spokesperson was asked about the WHO’s advice for fully vaccinated people by the New York Times. Referring to the CDC’s existing guidelines, the spokesperson said those recommendations would not be altered.

The CDC updated its guidance that fully vaccinated people do not need to wear a mask or socially distance in most situations in mid-May, before the highly contagious Delta variant, which was first identified in India, was widely circulating in the U.S.

The Delta variant is thought to be 40 to 60% more contagious than the Alpha variant, which was identified in the U.K. The Delta strain also poses a risk to unvaccinated and partially vaccinated people.

The CDC says unvaccinated people should continue wearing a mask in public indoor and outdoor settings.

The agency also says that unvaccinated people should follow other public health precautions, such as social distancing and staying in well-ventilated spaces. The story was published Tuesday in Scientific American.