The Delta coronavirus variant is surging across the United States and it appears to cause more severe illness and spread as easily as chickenpox, according to an internal document from the US Centers for Disease Control and Prevention.
The document outlines unpublished data that shows fully vaccinated people might spread the Delta variant at the same rate as unvaccinated people.
CDC Director Dr. Rochelle Walensky confirmed the authenticity of the document, which was first reported by The Washington Post.
“I think people need to understand that we’re not crying wolf here. This is serious,” she said.
“It’s one of the most transmissible viruses we know about. Measles, chickenpox, this — they’re all up there.”
Delta variant is about as transmissible as chickenpox, with each infected person, on average, infecting eight or nine others. The original lineage was about as transmissible as the common cold, with each infected person passing the virus to about two other people on average.
CDC was recommending that even fully vaccinated people wear masks indoors in places where transmission of the virus is sustained or high.
Including schools — students, staff and visitors should wear masks at all times.
When vaccinated people get infected, they have as much virus in their bodies as unvaccinated people. That means they’re as likely to infect someone else as unvaccinated people who get infected. But vaccinated people are safer, the document indicates.
“Vaccines prevent more than 90% of severe disease, but may be less effective at preventing infection or transmission,” it reads. “Therefore, more breakthrough and more community spread despite vaccination.”
It says vaccines reduce the risk of severe disease or death 10-fold and reduce the risk of infection three-fold.