Vaccine Info

V591 SARS-CoV-2 Vaccine

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Last reviewed
January 25, 2021

V591 SARS-CoV-2 Vaccine Description

Merck's V591 SARS-CoV-2 Vaccine candidate uses a measles virus vector platform to deliver the antigens to the immune system to spur antibody production against the SARS-CoV-2 virus.

Merck's Themis has a broad pipeline of vaccine candidates and immune-modulatory therapies developed using its innovative measles virus vector platform based on a vector originally developed by scientists at the Institut Pasteur, a world-leading European vaccine research institute, and licensed exclusively to Themis for select viral indications.

In March 2020, Themis joined a consortium and the Institut Pasteur and The Center for Vaccine Research at the University of Pittsburgh, supported by funding from the Coalition for Epidemic Preparedness Innovations, to develop a vaccine candidate targeting SARS-CoV-2 for the prevention of COVID-19.

On January 25, 2021, New Jersey-based Merck announced that the company is discontinuing the development of its SARS-CoV-2/COVID-19 vaccine candidates, V590 and V591. 

“We are grateful to our collaborators who worked with us on these vaccine candidates and to the volunteers in the trials,” said Dr. Dean Y. Li, president, Merck Research Laboratories. “We are resolute in our commitment to contribute to the global effort to relieve the burden of this pandemic on patients, health care systems, and communities.”

Merck, known as MSD outside of the United States and Canada, has been inventing for life, bringing forward medicines and vaccines for many of the world’s most challenging diseases in pursuit of our mission to save and improve lives. For more information, visit

V591 SARS-CoV-2 Vaccine Indication

V591 SARS-CoV-2 Vaccine is indicated to prevent COVID-19 disease caused by the SARS-CoV-2 coronavirus

    V591 SARS-CoV-2 Vaccine News

    January 25, 2021 - Merck (MSD) today announced that the company is discontinuing the development of its SARS-CoV-2/COVID-19 vaccine candidates, V590 and V591. This decision follows Merck’s review of findings from Phase 1 clinical studies for the vaccines. In these studies, both V590 and V591 were generally well-tolerated, but the immune responses were inferior to those seen following natural infection and those reported for other SARS-CoV-2/COVID-19 vaccines. Merck and its collaborators plan to submit the results of the Phase 1 studies for V590 and V591 for publication in a peer-reviewed journal.

    November 30, 2020 - Study: the bivalent MeV/SARS-CoV-2 vaccine candidate has several desirable properties concerning its immunogenicity and efficacy against SARS-CoV-2. Furthermore, the concurrent induction of anti-MeV immunity would allow its use in the context of routine measles immunization schedules.

    October 27, 2020 - Merck published COVID-19 Research Highlights.

    June 19, 2020 - Milestone Reflects Merck’s Commitment to Accelerate SARS-CoV-2 Vaccine Program.

    June 3, 2020 - The EU Malaria Fund has announced that it has approved to finance parts of the development of V591.

    May 26, 2020 - Merck and Themis announced that the companies have entered into a definitive agreement under which Merck, through a subsidiary, will acquire privately-held Themis.

    V591 SARS-CoV-2 Vaccine Clinical Trial

    Clinical Trial NCT04498247: A Study to Assess Safety, Tolerability, and Immunogenicity of V591 (COVID-19 Vaccine) in Healthy Participants (V591-001). Last Update Posted: December 7, 2020.

    • This early Phase 1 study's primary objective is to identify the V591 dose that achieves the target immune response in humans based on preclinical or early clinical data.
    • Participants in the 18 to 55-year-old sentinel cohort will receive 1 or 2 doses (Day 1 and Day 57) of V591 or placebo.
    • Estimated Study Completion Date: April 26, 2022.

    Clinical Trials

    No clinical trials found