Vaccine makers are leading studies using mRNA technology, which made the rapid development of COVID-19 vaccines possible, in hopes of creating more effective flu shots in the future, The New York Times reports. 

Each year there are between 3 and 5 million cases of severe illness from the flu worldwide, with up to 650,000 deaths. Flu shots are generally good for one influenza season, with effectiveness ranging between 40 and 60 percent, according to the Times’‘ Oct. 9 report. Still, in the 2018-19 flu season, when the shot had an effectiveness of just 29 percent, it prevented an estimated 4.4 million cases in the U.S., as well as 58,000 hospitalizations and 3,500 deaths, according to a study cited by the Times.

Five more notes on mRNA technology and flu vaccines: 

1. Traditional influenza shots take a while to produce and typically protect against four anticipated strains. They are grown for months in chicken eggs, and since it’s a slower process, scientists must select which strains to include several months before flu season, often leading to a mismatch by the time the actual strain arrives. Essentially, “It’s an educated guessing game,” Alicia Widge, MD, an immunologist at the National Institutes of Health’s Vaccine Research Center, told the Times. “We’re always catching up with the virus.” 

2. In contrast, mRNA vaccines are manufactured relatively quickly, potentially allowing scientists to better match the shots to each season’s flu strains. Researchers hope eventually the technology can be altered to make the flu shots work for a wider range of influenza strains or to develop a universal flu vaccine that offers protection for several years. 

3. Several vaccine makers, including Moderna and Pfizer, have recently started trials for mRNA flu vaccines. 

4. The technology could also enable vaccine makers to create combination shots more easily. In September, Moderna shared results from an experiment that showed combining mRNAs for seasonal flu, COVID-19 and respiratory syncytial virus produced high levels of antibodies for all three viruses in mice. 

5. If studies currently underway show mRNA flu shots improve effectiveness, it would still likely take years to gain approval because trials for the shots don’t have the government support that COVID-19 vaccines did. Federal regulators would also not consider them for emergency authorization, given the flu isn’t a novel threat and there are existing vaccines.