A reversal in federal health guidance calling for fully vaccinated individuals to don masks in certain indoor areas amid high and substantial viral spread has left some experts divided.
"In recent days, I have seen new scientific data from sequenced outbreak investigations showing that the delta variant behaves uniquely differently from past strains of the virus that cause COVID-19," Walensky told reporters over a call. "Information on the delta variant from several states and other countries indicate that in rare occasions, some vaccinated people infected with the delta variant after vaccination may be contagious and spread the virus to others."
However, the agency did not immediately release the data supporting the changed guidance.
"We anticipate the data being released soon," CDC spokesperson Kristen Nordlund told Fox News Thursday.
While some health experts like Dr. Kristin Englund with the Cleveland Clinic, and Dr. Gerald E. Harmon, president of the American Medical Association, embraced the guidance, calling the switch necessary to curb the spread of COVID-19 and the highly transmissible delta variant, others are less convinced.
Dr. Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security at the Bloomberg School of Public Health, told Fox News that the "puzzling" guidance likely won’t have a major impact on infections because unvaccinated individuals are largely driving transmission, and nearly all new hospitalizations and recent deaths are among those who had yet to receive shots.
"I think the focus needs to be on vaccines, not on masks for vaccinated individuals," Adalja said. "I don’t see that being a major way the trajectory of cases changes. If it’s a rare occurrence maybe contagious in a small number of people- how is that going to make a dent in transmission going on from unvaccinated [people]?"
"It’s strange to me that you would treat vaccinated and unvaccinated identically when the virus doesn’t treat them identically," he continued.
He suggested full FDA approval of COVID-19 vaccines could prompt many organizations and employers to mandate vaccines, thereby potentially boosting vaccine uptake. He went further, suggesting CDC advise school districts to mandate COVID-19 vaccines for teachers.
The highly transmissible delta variant is the predominant strain circulating in the U.S., with the variant detected in eight in 10 sequenced samples, Walensky noted on Tuesday. Englund, an infectious disease expert with the Cleveland Clinic, compared the rapid emergence and spread of the delta variant to a "wildfire," adding that advising masks for fully vaccinated populations in areas with substantial to high viral spread and other protective measures is a sound move.
"I think we’re learning every single day something new about this virus and this is a virus that has proven to us that it can change rapidly," Englund told Fox News. "We’ve seen from May until July, that the variant has gone from less than 1% up to 80% [in prevalence], so this can spread like a wildfire and we need to do everything that we can to stop it because if not, it will change again."
Americans should be flexible in regards to changing guidance, she said, given the emergence of the delta variant, adding, "Masking we know is extremely effective in decreasing the spread of coronavirus and that’s where we're going to need to be moving at this point."
Dr. Gerald E. Harmon, president of the AMA, which draws on over 190 state and specialty medical societies, issued a statement shortly after the CDC updated its guidance Tuesday, writing in part: "We strongly support the updated recommendations, which call for universal masking in areas of high or substantial COVID-19 transmission and in K-12 schools, to help reduce transmission of the virus. Wearing a mask is a small, but important protective measure that can help us all stay safer."
In a significant shift from prior guidance, the CDC on Tuesday also recommended "universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status."
Englund supported universal masking in schools, citing kids under 12 not yet eligible to receive COVID-19 vaccine, calling it "very important for all kids to get them safely back to school," while Johns Hopkins’ Adalja said the recommendations reflect the CDC’s effort to avoid another year of disrupted in-person schooling.