France’s Pasteur Institute announced Monday that it was midway abandoning its project of developing a COVID-19 vaccine following ineffective results. 

The private, non-profit institute named after its celebrated founder, Louis Pasteur, who invented the world's first vaccine in the 1880s, in a statement said it was halting development of the vaccine based on a measles vaccine following interim results from a Phase I clinical trial in humans.

“The vaccine candidate was well tolerated,” it said, “but the induced immune responses were found to be lower than those observed in people who recovered from a natural infection as well as those observed with authorized vaccines against SARS-CoV-2/COVID-19.”

The decision is a major blow to France’s effort to develop its own vaccine.

Last month, France’s biggest pharmaceutical company, Sanofi, announced that its vaccine candidate based on technology used to produce seasonal influenza vaccines and on immunological agents developed by Britain’s GSK will not be ready before the end of 2021. It said the delay was due to the interim results, which showed a low immune response in older adults.

In an unprecedented move last March, President Emmanuel Macron increased France’s scientific research budget by 5 billion euros over the next 10 years and set up an emergency fund of 50 million euros to finance the search for a vaccine against COVID-19.

The Coalition for Epidemic Preparedness Innovations (CEPI), a global alliance to develop vaccines, had funded the first stages of research and development of the Pasteur Institute’s COVID vaccine project. The vaccine used a measles virus combined with the antigens of the Spike protein of the SARS-CoV-2 virus.

The Phase I clinical trial was carried out last August in 90 healthy individuals at the institute’s centers in France and Belgium to test the safety and efficacy of the candidate vaccine.

The institute said its decision to abandon the anti-COVID vaccine does not affect two other vaccine candidate projects based on a nasal route and on DNA which are now in the preclinical phase.