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The big picture: Presentation slides from the agency leaked Thursday night showed that unpublished research indicated that the Delta variant causes more severe illness in unvaccinated people and spreads as easily as chickenpox.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.
What they found: Among the vaccinated with a breakthrough infection in Barnstable County, nearly 80% reported mild signs or symptoms, with the most common being cough, headache, sore throat, myalgia and fever.
- The people reported being in densely packed indoor and outdoor events at venues that included bars, restaurants, guest houses and rental homes.
- Five people were hospitalized, including one patient, who was middle-aged, unvaccinated, and had multiple underlying medical conditions. The remaining four adults were fully vaccinated, varied in age and, two had underlying medical conditions.
- As of July 27, no deaths were reported.
- A majority of the cases occurred in men with a median age of 40, but is likely due to the health department's sampling from the public events, which were marketed to adult male participants.
What they're saying: "This finding is concerning and was a pivotal discovery leading to CDC’s updated mask recommendation," CDC director Rochelle Walensky said in a statement Friday.
- "The masking recommendation was updated to ensure the vaccinated public would not unknowingly transmit virus to others, including their unvaccinated or immunocompromised loved ones," she added.