The U.S. Food and Drug Administration has approved a new messenger RNA (mRNA) flu vaccine, mFlusiva, developed by Moderna, which offers increased protection for adults aged 50 and older. Clinical trials indicated the new vaccine is 27% more effective than the standard flu shot.
The vaccine is fully approved for adults aged 50 to 64. For adults 65 and older, it has received accelerated approval while Moderna conducts an additional trial comparing mFlusiva to the current high-dose flu vaccine used for this age group. The new shot is expected to be available for the upcoming respiratory virus season, though insurance coverage details remain unclear.
The mRNA technology behind mFlusiva, familiar from its use in COVID-19 vaccines, allows for a more rapid vaccine production process. This is particularly beneficial given the influenza virus's tendency to change its genetic makeup, which can enable it to evade existing immunity, including from previous vaccines or natural infection. Each year, a new flu shot formulation is developed to target anticipated circulating strains. When the vaccine and the circulating virus strains do not match well, vaccine efficacy can be significantly reduced, leading to increased illness, hospitalizations, and deaths, as was observed during the 2022-2023 flu season, which was one of the worst in 25 years.
The mRNA platform allows for quicker adjustments to the vaccine to match evolving viral strains. Instead of redesigning the entire vaccine, manufacturers only need to modify a small part of the genetic blueprint. This nimbleness in manufacturing allows for a more responsive approach to circulating viruses.
As with any vaccine, mFlusiva may cause temporary, mild side effects such as fatigue, injection site soreness, headache, and low-grade fever. Individuals who experienced more pronounced reactions to mRNA COVID-19 vaccines might anticipate a similar or slightly stronger response to mFlusiva due to the shared technology. Clinical trials found these side effects were generally mild and lasted one to two days.
Experts emphasize that the most effective flu vaccine is the one an individual receives. If mFlusiva is not available when seeking vaccination, it is advisable to get the available flu shot to ensure timely protection against the virus. The development of mFlusiva represents a significant advancement in infectious disease prevention, building on the transformative impact of mRNA technology.