Trials to Test Vaccine Mixing With Booster Doses By Ralph Ellis July 1, 2021 -- Clinical trials are being conducted across the United States to see if giving fully vaccinated adults a different kind of booster dose is effective. One of the participating sites is the University of Pittsburgh School of Medicine, which is now recruiting volunteers. “As more and more COVID-19 variants are identified, we need to figure out how we, as a community, can stay protected,” Judy Martin, MS, a professor of pediatrics at the Pitt Medical School and a member of Pitt’s Center for Vaccine Research, said in a news release.