The first data from clinical trials of Moderna’s mRNA-based seasonal flu vaccine, released by the company Friday morning, were underwhelming — a finding that shows gene-based vaccines might not be a fix for all the problems with vaccine development.

The overwhelming success of the mRNA COVID-19 vaccines, made by Moderna and Pfizer / BioNTech, supercharged interest in that strategy for developing shots. The shots inject people with tiny snippets of the gene for a virus, which the body builds and then uses to learn how to fight the virus.

Current flu shots contain inactivated copies of the influenza virus. mRNA vaccines are faster to design and produce because manufacturers don’t have to grow copies of the virus, which is why experts have for years seen them as the future of vaccines.

Moderna launched a clinical trial of an mRNA seasonal flu vaccine this summer, hoping to capture the same success as it did with its COVID-19 vaccine. Typically, seasonal flu shots are around 40 to 60 percent effective, and pharmaceutical companies want to make that better. Three other companies are also working on mRNA flu shots.

Moderna released its first results during an investor phone call and presented slides showing that the mRNA flu shots did generate antibodies — but the levels of those antibodies weren’t higher than those for other flu shots already on the market. They also had more side effects than existing shots.

The findings don’t necessarily mean that mRNA flu shots aren’t any better than what we have now. Because mRNA vaccines are faster to design and make, the shots don’t have to be developed as far in advance. Companies may not have to do as much guesswork around what strain of the flu to target them against each year because they can wait to make the shots until they see what strains are circulating.

And as far as efficacy goes, there’s still a lot more data to collect: Moderna is preparing to conduct larger trials that would test how well the shots actually keep people from getting sick in the real world (not just testing antibody levels)..

Still, this early data shows that the immune system is tricky and that mRNA vaccines probably aren’t an easy shortcut for stopping a virus as persistent as the flu. More studies will be needed to figure out if there is a specific benefit to using mRNA vaccines to fight the flu, wrote chemist and writer Derek Lowe in Science. But it’s not a sure thing.

By Nicole Wetsman

Source: Moderna data shows mRNA isn’t a quick fix for the flu vaccine – The Verge

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