New vaccine demonstrates strong protection against severe Covid-19 in clinical trials

European drug makers Sanofi and GSK announced positive results from late-stage clinical testing of a new vaccine that will be named Vidprevtyn, according to a Sanofi spokesperson. The companies plan to seek authorization for the shots in the US and Europe.

Vidprevtyn is a protein subunit vaccine, which means it uses harmless protein fragments that teach the immune system how to spot and fight off the SARS-CoV-2 virus. It’s a more traditional type of vaccine than mRNA or adenovirus vector vaccines, which carry the genetic instructions for making the spike protein into cells, where they can then be built and displayed like mug shots for the immune system find and defend against.

These kinds of vaccines can be stored at refrigerator temperatures, making them easier to use in areas that don’t have access to ultracold storage. Because they rely on more familiar technology, there’s hope that people who’ve declined other kinds of Covid-19 vaccines may find these kinds of vaccines more palatable.

The vaccine is given in two doses delivered about three weeks apart. The phase 3 trials to test the vaccine enrolled more than 10,000 adults in the US, Asia, Africa and Latin America. A separate study is assessing a third dose of the vaccine as a booster.

After two doses given to people with no antibodies against the SARS-CoV-2 virus, the vaccine was:

  • 58% effective at preventing Covid-19 symptoms
  • 75% effective at preventing moderate or severe Covid-19
  • 100% effective against severe Covid-19 disease, including hospitalizations

The new vaccine posted lower numbers against symptomatic illness than the mRNA vaccines made by Pfizer and Moderna, but it was also tested under different conditions, when the new variants were circulating.

“We’re very pleased with these data,” said Thomas Triomphe, an executive vice president at Sanofi. “No other global Phase 3 efficacy study has been undertaken during this period with so many variants of concern, including Omicron, and these efficacy data are similar to recent clinical data from authorized vaccines.”

The companies said the vaccine performed well on its own and as a mix-and-match booster, bumping neutralizing antibodies by 18- to 30-fold when given to people who’d gotten Pfizer, Moderna or adenovirus-vector vaccines like the Johnson & Johnson and AstraZeneca shots. The manufacturers say there were no safety issues identified in the trials.

A company spokesperson says that the most likely role for the vaccine in the US and European markets — where so many people have completed their initial vaccine series — will be as a booster.

Millions of doses already released

The top-line study results were posted in company news releases. The manufacturers say full results from the trials will be published this year.

The vaccine was developed using $2.1 billion in funding from Operation Warp Speed, the landmark effort to speed effective vaccines against Covid-19 to the US and the rest of the world. The company says it has produced and released 100 million doses and plans to supply up to 400 million more doses.

Vidprevtyn development was delayed after results from an initial formulation showed that it didn’t generate a robust immune response in older adults. The companies reformulated and began testing again. The latest results come from a phase 3 trial started in May 2021 and reflect real-world tests of the shots against several variants, including Delta and Omicron, according to a Sanofi spokesperson.

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