The Paris-based company said it will continue to develop another vaccine candidate that is already undergoing late stage human trials.

That vaccine, developed jointly with the UK's GlaxoSmithKline, is based on the characteristic spike protein of the virus that causes COVID-19.

Messenger RNA vaccines use a different technology that uses genetic information from the virus to trigger an immune response.

This technology is already being used in the vaccines produced by Pfizer and Moderna.

"From a public health perspective, mRNA COVID vaccines are widely available today, and starting a placebo-controlled study in countries where vaccines are available would be extremely challenging, so it does not make sense for us to further advance our mRNA Covid vaccine into Phase 3," Sanofi said in response to questions from the Associated Press.

Sanofi recently expanded trials of its recombinant protein vaccine to test its effectiveness as a booster dose to extend immunity for people inoculated with a variety of other vaccines.

Results from that study are expected later this year.

While Sanofi has decided not to pursue a COVID-19 vaccine based on messenger RNA technology, the company said early testing showed "promising results".

As a result, Sanofi said it plans to use the technology to develop a new flu vaccine, with clinical studies expected to start next year.

"Today, we have a promising mRNA platform, which we're taking to the next level in development, including moving to modified mRNA, and against other diseases, including flu," Jean-Francois Toussaint, global head of research and development at Sanofi's vaccine unit, said in a statement.

Australian Associated Press