A nationwide study from the Centers for Disease Control and Prevention (CDC) has found that mRNA booster shots (either Pfizer or Moderna) are 82 percent effective in protecting against COVID-19 Omicron variant-associated emergency department (ED) visits and 90 percent effective in protecting against COVID-19 Omicron variant-related hospitalizations.

The value of the third dose of an mRNA vaccine is significant as two doses were only 38 percent effective in protecting against Omicron-related ED visits and only 57 percent effective in protecting against COVID-19 Omicron variant-related hospitalizations.

Boosters were even more effective against the Delta variant of COVID-19, protecting against 94 percent of both COVID-19 Delta variant associated ED visits and hospitalizations.

Our findings provide important evidence that booster shots are highly effective and those who are unvaccinated are at significantly greater risk of experiencing more severe COVID-19 outcomes and should get vaccinated and boostered as soon as possible. As we look at the high positivity rates across the nation, there is a silver lining. We have yet more evidence that vaccines and boosters offer protection against severe disease, including Omicron-related illness."

Shaun Grannis, MD, MS, Study Co-Author and Vice President for Data and Analytics at Regenstrief Institute

Grannis is also a professor of family medicine at Indiana University School of Medicine

"Effectiveness of a Third Dose 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" is published in the CDC's Morbidity and Mortality Weekly Report.

The U.S. Centers for Disease Control and Prevention (CDC) collaborated with six U.S. healthcare systems plus the Regenstrief Institute, to create the VISION network to assess COVID-19 vaccine effectiveness. In addition to Regenstrief Institute, other members are Columbia University Irving Medical Center, HealthPartners, Intermountain Healthcare, Kaiser Permanente Northern California, Kaiser Permanente Northwest and University of Colorado. Regenstrief contributes data and expertise to the VISION Network.