WASHINGTON, United States --People vaccinated against COVID-19 in high-risk parts of the United States should resume wearing masks indoors, the top health authority said Tuesday, a major shift in coronavirus guidance that underscores the country's struggle to suppress the Delta variant.
President Joe Biden said the announcement showed that America needs to "do better" on vaccinations, adding that a mandate for the country's more than two million federal workers was now "under consideration."
Centers for Disease Control and Prevention director Rochelle Walensky relayed the mask decision in a press call, citing new data that shows that while vaccines remain highly effective, rare breakthrough cases involving Delta have an increased risk of onward transmission.
"In areas with substantial and high transmission, CDC recommends fully vaccinated people wear masks in public indoor settings," she said.
According to the latest CDC data, much of the southern United States is experiencing high or substantial transmission, while highly vaccinated parts of the Northeast are mostly experiencing moderate rates of community transmission.
Substantial is defined as being between 50 to 100 daily cases per 100,000 people over a seven day average, while high is defined as more than 100 daily cases per 100,000.
In a statement following the move, Biden said he would lay out new steps on Thursday to overcome a lag in vaccinations, which have stalled badly for months despite the fact the United States has the highest supply of any country.
In a separate address to the US intelligence community, when asked about a possible vaccine mandate for US federal workers, Biden replied: "That's under consideration right now."
On Monday, the Veterans Affairs department said it would require its frontline health workers, some 115,000 people, to get the shot, becoming the first federal agency to institute the requirement.
- 'Temporary' measure -
Walensky stressed that so-called "breakthrough" cases among people who are vaccinated remain rare -- authorized shots reduce the risk of symptomatic disease seven-fold, and hospitalizations and deaths by a factor of twenty.
However, new CDC research showed that when a vaccinated person does become infected, their viral load is similar to an unvaccinated person.
"That leads us to believe that the breakthrough infections, rare as they are, have the potential to forward transmit at the same capacity of an unvaccinated person."
To stem the spread of the Delta variant, the CDC will recommend schools adopt universal masking, including teachers, staff, students and visitors -- regardless of vaccination status -- when they reopen in fall, she added.
As recently as last week, the CDC defended its May decision that vaccinated people do not have to wear masks indoors in most circumstances, with exceptions including public transit and hospitals.
But infection numbers are now swelling, thanks to the Delta variant, which accounts for around 90 percent of cases.
The latest seven day average of daily cases is more than 56,000, similar to levels last seen in April.
Forty-nine percent of the US population is fully vaccinated, but the vaccination rate is heavily skewed between politically liberal and conservative parts of the country.
Walensky stressed she saw masks as a "temporary" measure, adding: "What we really need to do to drive down these transmissions in areas of high transmission is to get more and more people vaccinated."
- Vaccines the solution -
Eric Cioe-Pena, director of Global Health at Northwell Health in New York, told AFP that rather than being a reflection of vaccines losing their efficacy, "this is a solution to a problem that exists because we have high levels of people that are not vaccinated."
"The main predictor of how much COVID is going to surge in an area is the vaccination rate," he added, so areas that are highly vaccinated will be de facto exempted from the new guidance.
According to a recent paper in the journal Virological, the amount of virus found in the first tests of patients with the Delta variant was 1,000 times higher than patients in the first wave of the virus in 2020, greatly increasing its contagiousness.
Last month, Israel reinstituted mask mandates, just 10 days after lifting them, due to the Delta variant, and local US jurisdictions, including Los Angeles County, have taken similar steps.