The nation’s top health officials announced Wednesday that the Biden administration is prepared to begin rolling out booster shots for many Americans the week of Sept. 20th. Citing data that show the effectiveness of Pfizer and Moderna vaccines against COVID-19 diminishes over time, U.S. Surgeon General Vivek Murthy said at a White House briefing: “Having reviewed the most current data, it is now our clinical judgment that the time to lay out a plan for COVID-19 boosters is now.” A final plan was still contingent upon the official sign-off by the U.S. Food and Drug Administration.

The recommendation will be that anyone who received Pfizer or Moderna vaccines should get a booster shot eight months after their second shot, with health care workers, nursing home residents and seniors first in line.  CDC Director Rochelle Walensky said at the briefing that Wednesday’s decision was largely based on data showing that vaccines are still working and are the best assurances against severe illness or death — but according to CDC data, key metric could also wane in a few months.  Walensky added: “Even though our vaccines are currently working well to prevent hospitalizations, we are seeing concerning evidence of waning vaccine effectiveness over time and against the delta variant. Given this body of evidence, we are concerned that the current strong protection against severe infection, hospitalization and death could decrease in the months ahead, especially among those who are at higher risk or who were vaccinated earlier during the phase of our vaccination rollout.”