The World Health Organization has urged fully vaccinated people to keep wearing their face masks indoors and practice social distancing — and now experts are weighing in.

But Dr. Shad Marvasti, who works at the University of Arizona College of Medicine-Phoenix, recently told Yahoo Finance why bringing back masks is a good idea.

  • “We don’t want to wait until after the fact and get caught with this thing already ahead of us when we know that masks work,” Marvasti told Yahoo Finance Live. “To put this in context, the alpha variant, which originated out of the U.K., was about 50% more infectious and transmissible. The delta variant is 60% more infectious than that.”

What does the CDC say?

Despite the WHO’s recommendation, the Centers for Disease Control and Prevention has not changed its mind about calling for face masks. Currently, the CDC says that fully vaccinated people do not need to wear face masks in most settings.

  • “If you are fully vaccinated, you are protected, and you can start doing the things that you stopped doing because of the pandemic,” CDC Director Dr. Rochelle Walensky said at a White House press briefing, per ABC News.
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Marvasti said the CDC should work to bring its face mask recommendation back to avoid a potential spike down the road.

  • “The CDC needs to act quickly, without waiting, to follow the WHO guidelines and ask everyone to put the masks back on so we can stay open, protect folks, and keep the economy going,” Marvasti said. “We’re already seeing preliminary numbers out of Israel where fully vaccinated people are getting sick.”

Why would we wear face masks again?

Other countries have added restrictions and face mask mandates as the delta variant has been rising. According to NPR, countries like Australia and Israel — as well as many in Europe — have added lockdowns and restrictions to deal with delta variant outbreaks.