The nation's top public health official, Rochelle Walensky, director of the Centers for Disease Control and Prevention, CDC, said vaccinated individuals may be able to spread COVID-19 and should resume wearing masks in certain conditions.

The CDC recommends that people who live in high-transmission communities wear masks in indoor public spaces, even if they've been vaccinated.

The agency also has recommended wearing masks for teachers, staff members and students in schools, even if they're fully vaccinated.

The new guidance has come as coronavirus cases have dramatically spiked during the summer months of July and August, according to the CDC Data Tracker. With this new surge in infections from the more transmissible Delta variant, more public and private organizations have put in place vaccine mandates.

Dr. Walensky described the delta variant, as practically a different virus, with the ability to cause infection flare-ups even among the fully vaccinated. "The delta variant is showing every day its willingness to outsmart us and to be an opportunist in areas where we have not shown a fortified response against it," she said.

This new CDC guidance on mask wearing for the fully vaccinated, changes course from the agency's May 13 guidance that vaccinated individuals had more protection from the coronavirus vaccines, and therefore did not require mask wearing indoors or outdoors.

"Vaccinated people are transmitting it, and the extent is unclear, but there's no doubt they're transmitting it," Dr. Anthony Fauci, President Biden's chief medical adviser said in an interview. "The situation has clearly changed", Fauci said. "People who are vaccinated, even when they're asymptomatic, can transmit the virus, which is the scientific foundation of why this recommendation is being made."

The agency's updated guidance has been largely welcomed by the medical and public health community, many of whom had appealed for more stringent mask wearing.

Many medical experts hope the new mask guidance will motivate more local officials to impose mask mandates, now that they have backing from the CDC.

Other nations around the world have reinstated indoor mask mandates as well. Israel reinstated their indoor mask mandate on June 25th due to the surge in Delta variant cases. During the summer, Australia and France have also put in place mask wearing rules in certain geographical locations as the Delta variant continues to surge.

South Korea has also mandated fully vaccinated people to wear masks indoors and outdoors, specifically in Seoul and surrounding areas. Read the full article from The Washington Post here.