IDCRC researchers are exploring the possible benefits of pairing doses from two different COVID-19 vaccines

Heterologous Prime Boost, Mix & Match Study

Researchers from Infectious Diseases Clinical Research Consortium (IDCRC) sites across the country are conducting a clinical trial to assess the use of booster doses of the Moderna-mRNA-1273 COVID-19 vaccine to determine the safety and effects of a mix and match booster on a person’s immunity to SARS-CoV-2, the virus that causes COVID-19.

The study will include two groups: persons who have already received any FDA emergency use authorized (EUA) COVID-19 vaccine and persons who have never received a COVID-19 vaccine and have not had a prior SARS-CoV-2 infection. Study participants will receive a delayed booster vaccine of Moderna-mRNA-1273, regardless of which COVID-19 vaccine was first administered - creating a mix and match booster.

“Delivering a different COVID vaccine as a booster - mixing and matching - might trigger potent immune responses. Pairing different vaccine platforms might work better than using the same one. This trial will help us assess and see how well the mix and match approach works,” says Robert Atmar, MD, professor of infectious diseases, Baylor College of Medicine and study co-principal investigator.

The study is being conducted by the IDCRC in collaboration with the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health.

This study will enroll approximately 400 healthy individuals ages 18 and older in the United States. The number of participants may increase with the addition of groups based on vaccines newly awarded EUA.

“Mix and match is not a new approach – it is a well-known principle in vaccine science research. Mixing vaccine platforms can elicit a stronger, longer-lasting response than a single vaccine regimen and could help us fight variants. This trial will help us assess,” says Kirsten E. Lyke, MD, professor of medicine, University of Maryland School of Medicine and study co-principal investigator.

Participating IDCRC Sites:

  • Baylor College of Medicine Vaccine and Treatment Evaluation Unit (VTEU)
  • University of Texas Medical Branch at Galveston, subsite of Baylor VTEU
  • Cincinnati Children’s Hospital Medical Center VTEU
  • Emory University VTEU
  • Kaiser Permanente Washington Health Research Institute VTEU
  • University of Rochester VTEU
  • New York University VTEU
  • University of Washington VTEU
  • University of Pittsburgh, subsite of Vanderbilt VTEU

Visit for additional details.

This activity is supported by the Infectious Diseases Clinical Research Consortium (IDCRC) through the National Institute of Allergy and Infectious Diseases (NIAID) (UM1AI148684). The IDCRC, consisting of the Vaccine Treatment and Evaluation Units (VTEUs) and the IDCRC Leadership Group, was formed in 2019 to support the planning and implementation of infectious diseases clinical research that efficiently addresses the scientific priorities of NIAID.  The consortium includes infectious diseases leaders and clinical researchers from Emory University, University of Maryland School of Medicine, Baylor College of Medicine, Cincinnati Children’s Medical Center and University of Cincinnati, FHI360, Fred Hutchinson Cancer Research Center, Johns Hopkins University, Kaiser Permanente Washington Health Research Institute, New York University, Saint Louis University, Vanderbilt University Medical Center, University of Alabama at Birmingham, University of Rochester, University of Washington, and NIAID. For more information about the IDCRC, please visit

Read more: Clinical Trial Evaluating Mixed COVID-19 Vaccine Schedules Begins