Coronavirus pandemic
The Washington PostDemocracy Dies in Darkness

How CDC data problems put the U.S. behind on the delta variant

Critics say the CDC’s failure to share real-time data led to overly rosy assessments of vaccine effectiveness — and complacency on the part of many Americans

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August 19, 2021 at 1:24 p.m. EDT
Nearly seven months into her tenure as the director of the Centers for Disease Control and Prevention, Rochelle Walensky is pressing to speed up the release of data. (Stefani Reynolds/New York Times/AP)

When Pfizer representatives met with senior U.S. government health officials on July 12, they laid out why they thought booster shots would soon be necessary in the United States. Data from Israel showed the vaccine’s effectiveness waned over time, especially in older and immunocompromised people.

But officials from the Centers for Disease Control and Prevention disagreed, saying their own data showed something quite different, according to four people with direct knowledge of the meeting who spoke on the condition of anonymity.