Thread by @BuzzFeedNews

A COVID outbreak among vaccinated people in Cape Cod is what prompted the CDC to say vaccinated people should mask up, too. buzzfeednews.com/article/stepha…

The Delta variant outbreak overwhelmingly led to mild cases among vaccinated people, showing that the vaccines still did their main jobs of preventing severe disease and death.

But these "breakthrough cases" could still spread the virus.

Outside experts reached by BuzzFeed News largely supported the CDC’s decision, arguing that the findings only add more urgency to speed up the nation’s vaccination campaign.

But some scientists are skeptical that the new CDC results can be interpreted very broadly. Bhattacharya called it “immunologically unlikely” that breakthrough cases were as contagious as infections in unvaccinated people. buzzfeednews.com/article/stepha…