CDC warns of a "significant decline" in vaccine effectiveness for some, prompting booster dose decision

New data released Wednesday by the Centers for Disease Control and Prevention warns of a "significant decline" in vaccine effectiveness against infection from COVID-19 in nursing home residents, as the highly contagious Delta variant of the virus causes a spike in hospitalizations among mostly unvaccinated Americans.

The release came as the Biden administration says it is preparing to offer booster shots for all Americans who got the Pfizer or Moderna vaccines, eight months after their second dose, beginning the week of September 20. "Based on our latest assessment, the current protection against severe disease, hospitalization, and death could diminish in the months ahead, especially among those who are at higher risk or were vaccinated during the earlier phases of the vaccination rollout," top federal health officials said in a joint statement on Wednesday.