corona virus-Covid19

CDC: Effectiveness of COVID-19 Booster Wanes with Time But Still Best Protection Against Severe Illness Interview with:
Dr. Mark G. Thompson, PhD
Deputy Chief – Science
COVID-19 Response Team
CDC Influenza Division  What is the background for this study? 

  • Protection against COVID-19 after 2 doses of mRNA vaccine (Pfizer-BioNTech or Moderna) wanes, but little is known about durability of protection after 3 doses.
  • CDC conducted a multistate analysis of emergency department (ED) visits, urgent care (UC) visits, and hospitalizations from August 26, 2021–January 22, 2022. Among adults who had either received two or three doses of an mRNA COVID-19 vaccine, effectiveness waned over time.  What are the main findings?

  • Getting a third dose was still highly effective at preventing COVID-19 hospitalizations during this period. Vaccine effectiveness (VE) waned over time since receiving the second dose, increased after getting a third dose, and then waned over time since getting a third dose. During the Omicron period, VE against hospitalization was 91% during the first 2 months after a third dose and decreased to 78% after more than 4 months. Comparatively, VE against ED/UC visits was 87% during the first two months after a third dose and decreased to 66% after 4 to 5 months. Overall, VE was higher for protection against hospitalizations than against ED/UC visits. Although protection waned with time, these findings show receipt of a third dose of mRNA vaccines remains highly effective at preventing severe COVID-19.  All people should remain up to date with recommended COVID-19 vaccinations to best protect against severe illness with COVID-19. What should readers take away from your report?

  • COVID-19 boosters are effective, and CDC continues to recommend everyone 5 and older remain up to date with recommended COVID-19 vaccinations, to ensure the best possible protection against severe COVID-19 illness. For most people, that means getting a booster dose 5 months after receiving an mRNA vaccine or 2 months after receiving Johnson and Johnson’s Janssen vaccine.
  • CDC is continuing to closely monitor the effectiveness of COVID-19 vaccines to help inform public health efforts. What recommendations do you have for future research as a result of this work?

No disclosures:


Ferdinands JM, Rao S, Dixon BE, et al. Waning 2-Dose and 3-Dose Effectiveness of mRNA Vaccines Against COVID-19–Associated Emergency Department and Urgent Care Encounters and Hospitalizations Among Adults During Periods of Delta and Omicron Variant Predominance — VISION Network, 10 States, August 2021–January 2022. MMWR Morb Mortal Wkly Rep. ePub: 11 February 2022. DOI: 

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Last Updated on February 14, 2022 by Marie Benz MD FAAD