• C Buddy Creech, Evan Anderson, Vladimir Berthaud, Inci Yildirim, Andrew M Atz, Ivan Melendez Baez, Daniel Finkelstein, Paul Pickrell, Judith Kirstein, Clifford Yut, Ronald Blair, Robert A Clifford, Michael Dunn, James D Campbell, David C Montefiori, Joanne E Tomassini, Xiaoping Zhao, Weiping Deng, Honghong Zhou, Daniela Ramirez Schrempp, Kelly Hautzinger, Bethany Girard, Karen Slobod, Roderick McPhee, Rolando Pajon, Rituparna Das, Jacqueline M Miller, Sabine Schnyder Ghamloush, and KidCOVE Study Group.
• From the Vanderbilt Vaccine Research Program, Department of Pediatrics, Vanderbilt University Medical Center (C.B.C.), and Meharry Medical College (V.B.) - both in Nashville; the Center for Childhood Infections and Vaccines of Children's Healthcare of Atlanta and the Department of Pediatrics, Emory University School of Medicine - both in Atlanta (E.A.); the Department of Pediatrics, Yale School of Medicine, the Department of Epidemiology of Microbial Diseases, Yale School of Public Health, and the Yale Institute for Global Health - all in New Haven, CT (I.Y.); the Medical University of South Carolina (A.M.A.) and Coastal Pediatric Associates (R.A.C.) - both in Charleston; Boca Raton Clinical Research Global, Edinburg (I.M.B.), Tekton Research, Austin (P.P.), Highland Woods Health, The Woodlands (C.Y.), Texas Health Care, Privia Medical Group-North Texas, Fort Worth, and Forest Lane Pediatrics, Dallas (R.B.) - all in Texas; Capitol Medical Group, Chevy Chase (D.F.), and the Department of Pediatrics, Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore (J.D.C.) - both in Maryland; Privia Medical Group, Arlington, VA (D.F., C.Y.); Velocity Clinical Research, Banning, CA (J.K.); Javara, Winston-Salem (C.Y., R.B.), and the Department of Surgery, Duke University Medical Center, Durham (D.C.M.) - both in North Carolina; Quality Clinical Research, Omaha, NE (M.D.); and Moderna, Cambridge, MA (J.E.T., X.Z., W.D., H.Z., D.R.S., K.H., B.G., K.S., R.M., R.P., R.D., J.M.M., S.S.G.).
• N. Engl. J. Med. 2022 May 26; 386 (21): 201120232011-2023.

BackgroundVaccination of children to prevent coronavirus disease 2019 (Covid-19) is an urgent public health need. The safety, immunogenicity, and efficacy of the mRNA-1273 vaccine in children 6 to 11 years of age are unknown.MethodsPart 1 of this ongoing phase 2-3 trial was open label for dose selection; part 2 was an observer-blinded, placebo-controlled expansion evaluation of the selected dose. In part 2, we randomly assigned children (6 to 11 years of age) in a 3:1 ratio to receive two injections of mRNA-1273 (50 μg each) or placebo, administered 28 days apart. The primary objectives were evaluation of the safety of the vaccine in children and the noninferiority of the immune response in these children to that in young adults (18 to 25 years of age) in a related phase 3 trial. Secondary objectives included determination of the incidences of confirmed Covid-19 and severe acute respiratory syndrome coronavirus 2 infection, regardless of symptoms. Interim analysis results are reported.ResultsIn part 1 of the trial, 751 children received 50-μg or 100-μg injections of the mRNA-1273 vaccine, and on the basis of safety and immunogenicity results, the 50-μg dose level was selected for part 2. In part 2 of the trial, 4016 children were randomly assigned to receive two injections of mRNA-1273 (50 μg each) or placebo and were followed for a median of 82 days (interquartile range, 14 to 94) after the first injection. This dose level was associated with mainly low-grade, transient adverse events, most commonly injection-site pain, headache, and fatigue. No vaccine-related serious adverse events, multisystem inflammatory syndrome in children, myocarditis, or pericarditis were reported as of the data-cutoff date. One month after the second injection (day 57), the neutralizing antibody titer in children who received mRNA-1273 at a 50-μg level was 1610 (95% confidence interval [CI], 1457 to 1780), as compared with 1300 (95% CI, 1171 to 1443) at the 100-μg level in young adults, with serologic responses in at least 99.0% of the participants in both age groups, findings that met the prespecified noninferiority success criterion. Estimated vaccine efficacy was 88.0% (95% CI, 70.0 to 95.8) against Covid-19 occurring 14 days or more after the first injection, at a time when B.1.617.2 (delta) was the dominant circulating variant.ConclusionsTwo 50-μg doses of the mRNA-1273 vaccine were found to be safe and effective in inducing immune responses and preventing Covid-19 in children 6 to 11 years of age; these responses were noninferior to those in young adults. (Funded by the Biomedical Advanced Research and Development Authority and the National Institute of Allergy and Infectious Diseases; KidCOVE ClinicalTrials.gov number, NCT04796896.).Copyright © 2022 Massachusetts Medical Society.

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