The documents appear to be talking points for CDC staff to use in explaining the dangers of the delta variant and “breakthrough″ infections that can occur after vaccination. The CDC has always expected some breakthrough infections but has struggled with how to explain them to the public. The internal documents also cite studies from Canada, Singapore and Scotland showing that the delta variant may pose a greater risk for hospitalization, intensive care treatment and death than the alpha variant, first detected in the United Kingdom. That trend coincides with the spread of the delta variant. But the CDC emphasizes that breakthrough infections are still uncommon.

Source: ABC News July 30, 2021 14:59 UTC