But some studies suggest that mRNA vaccines might prove more potent than traditional ones. In animal studies, mRNA vaccines seem to provide a broader defense against influenza viruses. They prompt the animals’ immune systems to make antibodies against the virus, and also train immune cells to attack infected cells.

But perhaps most important for the flu, mRNA vaccines can be made rapidly. The speed of mRNA manufacturing may allow vaccine makers to wait a few extra months before picking which influenza strains to use, potentially leading to a better match.

“If you could guarantee 80 percent every year, I think that would be a major public health benefit,” said Dr. Philip Dormitzer, Pfizer’s chief scientific officer.

The technology also makes it easier for mRNA vaccine makers to create combination shots. Along with mRNA molecules for different strains of influenza, they can also add mRNA molecules for entirely different respiratory diseases.