When American experts first started to worry that COVID-19 vaccines weren’t working quite as well against delta as they did against earlier coronavirus strains, they didn’t have much domestic data to go on. The Centers for Disease Control and Prevention was only collecting data on post-vaccination COVID-19 cases if they led to hospitalization or death — the agency wasn’t doing big-picture tracking of COVID-19 in vaccinated people. Only a few states and counties were collecting and publicizing that information.
The CDC was doing some analysis, but it wasn’t sharing the information quickly, frustrating experts who hoped for a more dynamic picture of how the delta variant was affecting vaccinated people. The agency finally released some…
