“Critics lament that the most up-to-date data about the delta variant has come from other countries, such as Israel, Great Britain and Singapore. And they say the CDC’s inability to share real-time information led top administration officials, including the president himself, to offer overly rosy assessments of the vaccines’ effectiveness against delta that may have lulled Americans intoa false sense of security”
https://www.washingtonpost.com/health/2021/08/18/cdc-data-delay-delta-variant/