New mRNA Flu Vaccine Offers Higher Efficacy for Adults 50 and Older
The FDA has approved Moderna's mRNA flu shot, mFLUSIVA, for people aged 50 and above, showing about 30% greater effectiveness than the traditional inactivated vaccine.
Seattle health officials said the 2026-2027 flu season is starting with higher-than-usual activity, though still within normal seasonal limits, according to the Washington State Department of Health.
Moderna's mRNA influenza vaccine, branded mFLUSIVA, received FDA approval for use in adults 50 years and older. The vaccine was tested in clinical trials involving that age group and demonstrated roughly a 30% increase in effectiveness compared with the standard inactivated flu shot.
"I’ve been working on them for over 30 years, just understanding how they work," said Dr. Deborah Fuller, a microbiology professor at the University of Washington School of Medicine.
Dr. Fuller explained that mRNA vaccines trigger both antibody production and a T-cell response, providing an additional layer of immune protection. She noted that older adults often have weaker immune responses to conventional flu vaccines, which rely on inactivated virus strains that must be selected months in advance.
Traditional flu vaccines use inactivated virus strains and require a six-month development window, during which circulating flu viruses can mutate, potentially reducing vaccine match and effectiveness. In contrast, mRNA technology allows for faster production, enabling a closer match to the strains circulating at the time of vaccination.
"They are very good, especially among the younger people under 50 years old. Your immune system is very robust and able to respond to those vaccines," Fuller added, emphasizing that standard flu shots remain effective for younger populations.
Addressing lingering concerns about mRNA technology, Dr. Fuller said the vaccines have been administered to millions across diverse demographics, including immunocompromised individuals, and have been thoroughly vetted for safety.
The new vaccine offers an alternative for older adults who are at higher risk of severe flu complications, while health officials continue to recommend the conventional flu shot for those under 50.