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July 07, 2021

The mRNA technology used in COVID-19 shots may yield a more effective flu vaccine

Scientists say adopting a new approach would eliminate the annual guesswork that goes into influenza immunizations

The COVID-19 vaccines produced by Pfizer and Moderna utilize synthetic messenger RNA, a technology that was considered experimental prior to the pandemic. 

With the shots successfully reducing the risk of illness, researchers now are considering applying it to the fight against other viruses, including influenza. 

In the COVID-19 vaccines, the mRNA instructs cells to make copies of the coronavirus's distinctive spike protein, triggering an immune response without any direct contact with the virus.

By contrast, most flu shots are developed by growing influenza viruses in mammalian cells or chicken eggs. The viruses are then killed or inactivated. The resulting proteins trigger the body's immune response when the vaccine is administered. 

But it can take up to six months to develop each year's vaccine. And the vaccines usually are only 40-60% effective because scientists have to make an educated guess about which flu strains will be the most dominant in the upcoming season. 

An mRNA vaccine, on the other hand, can be developed less than a month after the genetic sequence of a new flu strain is identified, The Verge reported

And since mRNA vaccines use synthetically-produced genetic material rather than live viruses, scientists say they could wait to identify the most dominant flu strains before developing the vaccine each year. That way, the vaccine would be a better match, improving its efficacy. 

Moderna announced Wednesday that it had begun dosing volunteers in a study of a potential mRNA flu vaccine. Sanofi and Translate Bio previously had begun clinical trials on an mRNA flu vaccine. And Pfizer and BioNTech first announced plans for such a shot in 2018. 

Moderna CEO Stéphane Bancel said the pharmaceutical company hopes to eventually create vaccines that can target multiple viruses, including the flu, RSV and COVID-19, in one shot. 

"Our vision is to develop an mRNA combination vaccine so that people can get one shot each fall for high efficacy protection against the most problematic respiratory viruses," Bancel said in a statement. "We look forward to advancing our core modality of prophylactic mRNA vaccines so that we can continue to make an impact on global public health."

The Centers for Disease Control and Prevention estimates that influenza causes 9 million to 45 million illness each year. It has accounted for 810,000 hospitalizations and 12,000 to 61,000 deaths annually since 2010.

"It always a bit of lottery each year when the flu vaccine comes out," Pfizer Chief Scientific Officer Phil Dormitzer previously said. "There's always concern whether they're will be enough supply in time for the peak season and how well it’s going to work. If we are able to reduce or eliminate the mismatch we have from year to year, it would be a huge opportunity to help prevent influenza illness and death."

Dormitzer theorized that when people are injected with a mRNA flu shot, their muscle cells will turn into vaccine "factories," stimulating a strong immune response. He said it is an approach that more closely mimics what happens when a person's immune system is actually fighting an infection.

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