Fully vaccinated Americans should go back to masking up in schools and areas of high or substantial COVID-19 transmission, the Centers for Disease Control and Prevention announced Tuesday.

The CDC says its stark reversal in mask guidance is prompted by the current surge in COVID-19 cases and the spread of the hyper-transmissible delta variant, which is now dominant in the US and thought to be more than twice as contagious as previous versions of the virus.

Specifically, the CDC says new data from outbreak investigations in the US and elsewhere suggests that fully vaccinated people who have breakthrough infections with the delta variant carry similar levels of viral loads in their respiratory tracts as unvaccinated people infected with the delta variant. This raises concern that fully vaccinated people can spread the delta variant to others.

“The vast majority of transmission occurring [in the US] is occurring through unvaccinated individuals,” CDC Director Rochelle Walensky emphasized in a press briefing Tuesday. She also highlighted that “the vaccines continue to do an exceptional job at protecting the individual who is vaccinated from severe illness, hospitalization, and death, and even against mild illness.”

“But unlike the alpha variant that we had back in May, where we didn’t believe that if you were vaccinated you could transmit further, this is different now with the delta variant,” she said. And this new concern “unfortunately warrants an update to our recommendation.”

New recommendations

The CDC now recommends that all fully vaccinated people wear a mask in indoor public spaces when local COVID-19 transmission levels are “high” or “substantial.” The agency defines “high” transmission as more than 100 new cases of COVID-19 among 100,000 people in the course of seven days, while “substantial” is defined as 50 to 99 cases among 100,000 over seven days.

Those definitions currently apply to a large swath of the country. As of Tuesday, 46 percent of counties nationwide have high transmission levels, and an additional 17 percent of counties have substantial transmission, the CDC reports. All or nearly all counties in Arkansas, Louisiana, Florida, Missouri, and Mississippi are included. The southeastern US has generally become a hotbed of transmission in recent weeks, along with many areas in the Midwest. Many counties in several states have case rates well over 500 per 100,000 in the past seven days.

Additionally, the CDC is now recommending universal masking in all K-12 schools. That is, all teachers, staff, and students, regardless of vaccination status, should wear masks in schools.

As before, people who are unvaccinated or partially vaccinated—even those who have recovered from COVID-19—should continue to wear masks, practice social distancing, and get vaccinated as soon as possible. Anyone who has questions about the vaccines should consult their medical doctor.

The new recommendations for the fully vaccinated are a turnaround from the agency’s earlier guidance from May 13, which said that fully vaccinated people are extremely well protected from the pandemic coronavirus and no longer need to mask in most settings. That guidance, however, was seen as abrupt and premature and has been dogged by controversy since its announcement. Among the leading criticisms are that it is currently impossible to determine vaccination status in most settings, it put vulnerable people at risk, and it didn’t account for local conditions that could warrant more precautions, such as high transmission and low vaccination rates.

About face

In May, transmission levels were on the decline, and the delta variant had not taken hold of the US. Now, with delta dominating the country, cases are spiking nationwide. In the press briefing, Walensky said that the mask guidance will help drag down the transmission rate, which is critical for everyone—not just the unvaccinated.

As the pandemic virus has more opportunities to spread and infect people, it has more opportunities to mutate and evolve into yet more dastardly variants. Future variants, Walensky cautioned, could further thwart protection from vaccination.

In addition, the new mask guidance will not just protect those who are unwilling to get vaccinated but also those who are unable to be protected. That includes children who are still ineligible to get vaccinated and immunocompromised people who may not be well-protected.

In closing remarks, Walensky addressed the frustration she expects in response to the new guidance, given the length of the pandemic so far, mental health struggles, vaccine hesitancy that is causing preventable surges, and fully vaccinated people now being asked to again take mitigation efforts.

“It is not a welcomed piece of news that masking is going to be a part of people’s lives who have already been vaccinated,” she acknowledged. But she said experts that the CDC consulted “universally” supported the masking change. “This was not something that we took lightly, and it’s something that I know weighs heavily with me and with all of America.”

https://arstechnica.com/?p=1783521