A universal flu vaccine that could protect people against most influenza strains for years at a time has long been one of the most sought after goals in infectious disease research. A new study from the Perelman School of Medicine at the University of Pennsylvania, published in Nature Communications, brings that goal meaningfully closer. The candidate flu vaccine uses mRNA technology to elicit a powerful antibody response targeting a conserved region of the influenza virus, offering broad protection across multiple strains in animal models.
Why a Universal Flu Vaccine Has Been So Difficult to Develop
Current seasonal flu vaccines work by prompting the immune system to produce antibodies against the outermost head region of the hemagglutinin protein, a mushroom shaped structure found on the surface of flu virus particles. The problem is that this head region mutates rapidly, and the strains dominant in one flu season are often replaced by strains with different hemagglutinin head structures the following year. The result is that seasonal flu vaccines provide incomplete and temporary protection, which is why they must be reformulated and readministered annually.
Despite the widespread use of seasonal vaccines, influenza still causes millions of infections, hundreds of thousands of hospitalizations, and tens of thousands of deaths in the United States every year. A flu vaccine that targets a more stable part of the virus, one that does not change between strains, could change that picture dramatically.
How the mRNA Flu Vaccine Works Differently
The Penn flu vaccine does not use lab grown viral proteins directly. Instead, it uses modified mRNA molecules that instruct the body’s own immune cells to produce copies of the hemagglutinin protein internally. When injected, these mRNA molecules are taken up by dendritic cells and translated into viral protein copies using the cell’s own machinery. This internal production more closely mimics an actual flu infection and elicits a substantially stronger immune response than conventional protein based vaccines.
Critically, this approach generated robust antibodies against the lower stalk region of the hemagglutinin protein, an area that does not vary between flu subtypes and has long been considered the ideal target for a universal flu vaccine. Seasonal flu vaccines using hemagglutinin proteins directly have consistently failed to produce meaningful anti stalk responses. Two injections of the mRNA flu vaccine, given four weeks apart, produced strong and durable anti stalk antibodies in mice that persisted and even strengthened over the 30 week study period.
Flu Vaccine Protection Across Multiple Strains in Animal Models
The research team demonstrated that the antibody response generated by the mRNA flu vaccine translated into real protection against infection. Mice immunized with a vaccine encoding the H1 subtype survived exposure to otherwise lethal doses of three distinct flu strains: the matched H1 virus, a distantly related H1 strain, and an H5 strain. The experiments were successfully replicated in ferrets and rabbits, two additional animal models commonly used in vaccine development research.
According to co senior author Scott Hensley, PhD, the magnitude of the antibody response surprised the research team when testing first began. Co senior author Drew Weissman, MD, PhD, noted that the vaccine achieved something most other candidate flu vaccines have not: eliciting protective responses against a conserved region that offers genuinely broad protection across strains.
What Comes Next for the Universal Flu Vaccine
The research team plans to advance the mRNA flu vaccine into non human primate studies and then human clinical trials, with a target timeline of beginning trials within two years of the study’s publication. Large scale production of mRNA based vaccines is considered relatively straightforward, as a single reaction produces the mRNA and a second produces the lipid nanoparticles used to deliver it, making manufacturing scale up more feasible than with conventional vaccine platforms.
The researchers also noted that the mRNA platform could accommodate multiple hemagglutinin subtypes in a single flu vaccine formulation, further broadening protection. Combined with newly developed hemagglutinin stalk antigens, Weissman suggested the approach could form the basis of a highly effective universal flu vaccine. If it performs in humans even a fraction as well as it has in animal models, it could eventually replace annual flu shots with a durable, broad spectrum vaccine given only a few times over a lifetime.
To read more about infectious disease research and vaccine development, visit the FOMAT blog. FOMAT conducts infectious disease and vaccine clinical trials at sites across the United States. To learn more about active studies, visit FOMAT’s patient studies page.
For the full source, see the original article at R&D Magazine.Sonnet 4.6