US to say some vaccinated people need to mask again: reports
The US Centers for Disease Control and Prevention (CDC) is expected to issue new guidance Tuesday saying that people vaccinated against Covid-19 need to wear masks indoors in some circumstances, according to reports.
The shift comes as the Delta variant is driving a sharp surge in cases, with hotspots in regions that have lagged behind in vaccinations.
Top health officials huddled Sunday night to discuss the issue, according to CNN, and the change is expected to be announced at a briefing by CDC director Rochelle Walensky at 3:00 pm Eastern (1900 GMT). The Washington Post also reported the development.
As recently as last week the CDC defended its decision, announced in May, to say vaccinated people do not require masks indoors in most circumstances, with exceptions including public transit and hospitals.
But Delta, which now accounts for around 90 percent of new US infections, has changed the calculations.
While current vaccines remain highly effective against hospitalization and death, there are increased reports of breakthrough infections, making personal risk and the risk of transmission more closely linked to the level of virus circulating within a community.
Experts have suggested pegging mask use to local metrics such as the level of vaccination and Covid hospitalizations per capita, considered a more reliable measure of disease spread than cases per capita.
According to a recent paper in the journal Virological, the viral load in the first tests of patients with Delta was 1,000 times higher than patients in the first wave of the virus in 2020.
Not only does Delta replicate more rapidly inside its host compared to past strains, but people who are infected shed much more of it in the air, greatly increasing the likelihood it will be transmitted.
Last month, Israel reinstituted mask mandates just 10 days after lifting them, in light of the Delta variant and local US jurisdictions like Los Angeles County have taken similar steps.