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Pitt Enrolling Participants in Mixed COVID-19 Booster Shot Trial

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PITTSBURGH – The University of Pittsburgh School of Medicine, through the Pittsburgh Vaccine Trials Unit (PVTU), is one of twelve sites across the country selected to participate in a National Institute of Allergy and Infectious Diseases clinical trial in which fully vaccinated adults will receive a third “booster” dose of a COVID-19 vaccine. The trial will study the safety and immune response of a mixed-booster regimen. 


“As more and more COVID-19 variants are identified, we need to figure out how we, as a community, can stay protected,” explained Judy Martin, M.D., professor of pediatrics at the Pitt’s School of Medicine and member of Pitt’s Center for Vaccine Research. “The study’s design is not to show whether we need booster shots. Its focus is identifying which vaccine combinations are safe and provide the most protection against the virus that causes COVID-19 and its variants.”


The study is broken up into two cohorts:


  • One group will be comprised of about 150 fully vaccinated adults who received one of the three COVID-19 vaccines available in the U.S. under FDA Emergency Use Authorization: Johnson & Johnson’s Janssen COVID-19 vaccine, Moderna COVID-19 vaccine and Pfizer COVID-19 vaccine. Twelve to 20 weeks following their initial vaccination regimen, volunteers will receive a single booster dose of the Moderna COVID-19 vaccine.
  • Another group will be comprised of around 250 adults who have not received a COVID-19 vaccine. Volunteers will receive the two-dose Moderna COVID-19 vaccine regimen and will receive a booster dose of a vaccine about 12 to 20 weeks later. 


Throughout the year, the volunteer participants will provide blood samples, which will be used to study their immune response against new variants of COVID-19. If participants contract COVID-19 throughout the duration of the study, investigators will assess whether a COVID-19 variant caused the infection.


While study participants will be followed for a year, initial results are expected in late summer 2021.  


Other combinations of vaccines may be studied in the future as part of this research.


For more information on the Pittsburgh site of the trial, visit The identifier for this study is NCT04889209.