Scientists at the University of Pennsylvania have developed an experimental mRNA vaccine that protects against all known subtypes of the influenza virus. In total, the experimental multivalent vaccine protects against 20 influenza subtypes.
Current flu vaccines protect against several recently circulating strains but would not be expected to protect against an emerging pandemic influenza strain. Influenza viruses have the potential to cause pandemics with substantial death tolls. Notably, the 1918 “Spanish flu” pandemic killed at least 50 million people worldwide.
The 1918 “Spanish flu” pandemic was a result of an influenza virus that began circulating in birds and later jumped to humans. This allowed the virus to accumulate various mutations that made it highly pathogenic.
The experimental mRNA influenza vaccine developed at the University of Pennsylvania seeks to stimulate a broader immune response that could protect against novel pandemic influenza strains in the future. The experimental vaccine would elicit a memory immune response that could help the immune system fight a novel influenza strain. Still, it would not provide the type of sterilizing immunity that prevents a viral infection from occurring in the first place.
Senior study author Scott Hensley says that “it would be comparable to first-generation SARS-CoV-2 mRNA vaccines, which were targeted to the original Wuhan strain of the coronavirus. Against later variants such as Omicron, these original vaccines did not fully block viral infections, but they continue to provide durable protection against severe disease and death.”
Experimental results show that the multivalent vaccine was effective in eliciting the production of a key flu virus protein called the hemagglutinin protein. In mice, the vaccine led to high levels of antibodies which reacted strongly to all 20 flu subtypes and remained elevated for at least four months.
“The idea here is to have a vaccine that will give people a baseline level of immune memory to diverse flu strains so that there will be far less disease and death when the next flu pandemic occurs,” Hensley said.