U.S. health officials announced that Covid-19 booster shots will be offered to those who received two doses of the Pfizer or Moderna vaccine beginning the third week of September.
The announcement comes after the Centers for Disease Control and Prevention (CDC) published three studies indicating that vaccines’ effectiveness in preventing infections has decreased.
The data does not say that a third dose would be any more effective than the current two-dose series in preventing severe outcomes like hospitalization and death. Instead, the booster is designed as an offensive move against Covid-19 in advance of winter.
- Tenforde, M.W., Self, W.H., Naioti, E.A. (2021). Sustained effectiveness of Pfizer-BioNTech and Moderna vaccines against COVID-19 associated hospitalizations among adults — United States, March–July 2021. MMWR Morb Mortal Wkly Rep. doi: 10.15585/mmwr.mm7034e2. Retrieved from: https://www.cdc.gov/mmwr/volumes/70/wr/mm7034e2.htm?s_cid=mm7034e2_w