The World Health Organization said on Friday that fully vaccinated people should maintain social distance, including the use of masks, in order to prevent community transmission of the coronavirus’s delta variant.

The delta variant was discovered in India, where the coronavirus pandemic is still spreading and wreaking havoc on the population. It has since spread to the United States, where experts believe the delta variant is responsible for up to 20% of new coronavirus cases.

Dr. Mariangela Simao, WHO assistant director-general for access to medicines and health products, told reporters on Friday that social distancing needs to continue, even for those who are fully vaccinated.

“People cannot feel safe just because they had the two doses. They still need to protect themselves,” Simao said.

“Vaccine alone won’t stop community transmission,” Simao continued. “People need to continue to use masks consistently, be in ventilated spaces, hand hygiene… the physical distance, avoid crowding. This still continues to be extremely important, even if you’re vaccinated when you have a community transmission ongoing.”

On Thursday, President Joe Biden said in comments from Raleigh, North Carolina, that the emergence of the delta variant in the U.S. should encourage parents to get their children vaccinated.

“Six hundred thousand-plus Americans have died, and with this delta variant you know there’s going to be others as well. You know it’s going to happen,” he said. “We’ve got to get young people vaccinated.”

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