CDC: COVID-19 vaccine effectiveness diminished with rise of Delta variant

Editor's Note

In this study, Centers for Disease Control and Prevention (CDC) researches find that COVID-19 vaccine effectiveness in frontline workers diminished with the rise of the Delta variant.

Effectiveness of the COVID-19 vaccines declined to 66% after the Delta variant became dominant, compared with 91% before its spread.

The study tracked 4,136 healthcare workers, first responders, and other frontline personnel in eight US locations from December 2020 to August 2021. About two thirds received the Pfizer-BioNTech vaccine, 2% received Johnson & Johnson, and the rest received Moderna.

Though these interim findings show a reduction in the effectiveness of COVID-19 vaccines in preventing infection, a sustained two-thirds reduction in infection risk underscores the importance of COVID-19 vaccination, the researchers say.