Covid-19: vaccine against SARS-CoV-2 infection, using the measles vector

Phase I testing in humans for the Institut Pasteur's SARS-CoV-2 vaccine candidate using the measles vector under way since August 2020 in France and Belgium

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A Phase I clinical trial to assess the safety and immunogenicity of vaccine candidate TMV-083 (previously known as MV-SARS-CoV-2) began in France in August 2020. This is the first time the vaccine candidate, developed by Institut Pasteur scientists in partnership with Austrian biotech company Thémis and with the support of CEPI to tackle the COVID-19 epidemic, has been administered to humans.

See the press release "MV-SARS-CoV-2 vaccine candidate: A new partnership between Institut Pasteur, CEPI, Thémis and MSD."

Vaccine candidate TMV-083 is an attenuated live virus vaccine using the measles vaccine (MV) as a vector (or vehicle) and expressing a spike protein antigen from the SARS-CoV-2 virus. The spike protein, the "entry key" that allows the virus into cells, forms spikes all around the virus.

The Institut Pasteur is the sponsor of this clinical trial. The trial is being conducted partly at the Cochin-Pasteur Clinical Investigation Center (CIC) in Cochin Hospital (Paris Public Hospital Network – AP-HP) and partly in Belgium.

A total of 90 healthy volunteers will be taking part in the study. They will receive two doses of the vaccine candidate and/or a placebo. The two injections will be administered 28 days apart, the time needed to enable the immune system to identify and respond to the presence of the virus. The majority of the volunteers will be assessed on a double-blind basis, meaning that neither the doctors nor the volunteers themselves will know whether they have been given the vaccine candidate or the placebo.

The final results of the trial, including long-term monitoring of volunteers, are expected in 2021.

The measles vector, a promising technique

Vaccine candidate TMV-083 (previously known as MV-SARS-CoV-2) for SARS-CoV-2 draws on the Institut Pasteur's expertise in developing recombinant vaccines using the measles vector. The virus used in the measles vaccine is used here as a vector (or vehicle) for the development of recombinant vaccines expressing antigens from other pathogens (fragments of dengue, Lassa fever or other viruses responsible for emerging diseases). This approach was chosen to tackle the SARS-CoV-2 novel coronavirus because back in 2003, a previous vaccine candidate for the SARS-CoV-1 coronavirus, also designed by Institut Pasteur scientists using the measles vector, reached the clinical development stage after its efficacy was demonstrated on an animal model. But development of the vaccine was stopped after the beginning of Phase I because the outbreak of severe acute respiratory syndrome (SARS) (page in French), caused at the time by the SARS-CoV-1 virus, had come to an end.

The same method based on the measles vector has also been used to develop other vaccines. A vaccine candidate for chikungunya is set to enter Phase III and vaccines against infection with the Lassa, Zika and MERS viruses are also in development.

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