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New Vaccine With 100 Percent Efficacy Against Severe COVID-19 Seeks Approval


Dr. Katie Spalding

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory.

Freelance Writer

covid-19 vaccine 100 percent efficacy

The vaccine boasts an unbeatable 100 percent efficacy against severe disease and hospitalizations from COVID-19. Image credit: IFLScience

A new COVID-19 vaccine has achieved 100 percent efficacy against severe disease and hospitalizations, announced manufacturers Sanofi and GSK on Wednesday. The companies are now set to apply for regulatory authorization from bodies like the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) to release the vaccine as both a two-dose vaccine and booster shot.

Unlike vaccines based on mRNA technology, the new Sanofi-GSK offering is a protein-based vaccine – a “well-established approach that has been applied widely to prevent infection with other viruses including pandemic flu,” said GSK President Roger Connor in a statement today.


“We are confident that this vaccine can play an important role as we continue to address this pandemic and prepare for the post-pandemic period,” he added.

Like other COVID-19 vaccines, the idea behind the new dose is to target the spike protein of the SARS-CoV-2 virus which causes the disease. While mRNA vaccines work by feeding our own cells the information needed to make their own spikes to practice against, the Sanofi-GSK vaccine instead contains a modified version of the spike itself to impart immunity.

While the vaccine on its own is reported to have an efficacy rate of just 57.8 percent against any symptoms of the disease – much less than those reported for the mRNA vaccines produced by companies such as Pfizer and Moderna – the company boasts an unbeatable 100 percent efficacy against severe disease and hospitalizations, as well as 75 percent efficacy against moderate-to-severe disease.

“We’re very pleased with these data, which confirm our strong science and the benefits of our COVID-19 vaccine,” said Sanofi Executive Vice President Thomas Triomphe. “The Sanofi-GSK vaccine demonstrates a universal ability to boost all platforms and across all ages.”


Should it get regulatory approval, there are quite a few potential advantages to the Sanofi-GSK offering. Because it’s not mRNA-based, it can be produced inexpensively and stored at refrigerator temperatures rather than needing ultra-cold storage – good news for people in low-income countries where vaccine rollout has been desperately low.

It may also convince some vaccine-hesitant people to get the shot, since it’s based on older, more widely established technology.

And while the overall efficacy rate against any symptoms at all may not be up to mRNA-vaccine standards, neutralizing antibody levels increased after the Sanofi-GSK vaccine more than twice as much as its mRNA rivals.

This effect was even more marked when the Sanofi-GSK vaccine was used as a booster: in study participants who had previously had an alternative vaccine, a Sanofi-GSK booster shot increased neutralizing antibody levels by 18- to 30-fold across vaccine platforms and age groups, the statement reports.


For study participants whose initial vaccine regimen was Sanofi-GSK, this increase was an astonishing 84- to 153-fold.

“We… observed robust efficacy of the vaccine as a primary series in today’s challenging epidemiological environment,” said Triomphe. “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 the recent clinical data from authorized vaccines.”

Full data and results from the vaccine trial will be published later this year.


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