CDC: Delta variant may cause mild COVID among fully vaccinated people

About 74% of 469 COVID-19 cases associated with large gatherings held in Barnstable County, Mass., from July 3 to 17 were among fully vaccinated people, according to data released Friday from the Centers for Disease Control and Prevention.

Why it matters: The data bolsters emerging evidence that vaccinated people have high viral loads and may transmit the Delta variant as easily as those who are unvaccinated.

Be smart: Despite mild breakthrough cases appearing more common than previously thought, "vaccination is the most important strategy to prevent severe illness and death," the report emphasizes.

The big picture: Presentation slides from the agency leaked Thursday night showed that unpublished research indicated that the Delta variant causes more severe illness in unvaccinated people and spreads as easily as chickenpox.

On Tuesday, the CDC recommended people should wear masks in indoor public settings in areas where COVID-19 transmission is high or substantial regardless of vaccination status.