Page 1/21 Reactogenicity, Safety, and Serological and Cellular Immunogenicity of a Booster Dose of SARS-CoV-2 mRNA Prototype, Variant, and Bivalent Vaccines Evan J. Anderson Center for Childhood Infections and Vaccines (CCIV) of Children’s Healthcare of Atlanta and Emory University Department of Pediatrics, Department of Medicine, Emory University School of Medicine, Atlanta, GA USA Lisa A. Jackson Kaiser Permanente Washington Health Research Institute, Seattle, WA Nadine G. Rouphael Hope Clinic, Department of Medicine, Emory University School of Medicine, Decatur, GA Alicia T. Widge Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases (NIAID), NIH, Bethesda, MD David Monteｦori Duke Human Vaccine Institute and Department of Surgery, Duke University Medical Center, Durham, NC Nicole A. Doria-Rose Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases (NIAID), NIH, Bethesda, MD Mehul Suthar Center for Childhood Infections and Vaccines (CCIV) of Children’s Healthcare of Atlanta and Emory University Department of Pediatrics, Atlanta, GA USA and Emory Vaccine Center, Yerkes National Primate Research Center, Emory University School of Medicine, Atlanta, GA Kristen W. Cohen Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center; Department of Medicine and Laboratory Medicine and Pathology, University of Washington, Seattle, WA Sarah O’Connell Vaccine Research Center (VRC), National Institute of Allergy and Infectious Diseases (NIAID), NIH, Bethesda, MD Mat Makowski The Emmes Company, LLC, Rockville, MD Mamodikoe Makhene Division of Microbiology and Infectious Diseases, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Bethesda, MD