A universal flu vaccine is here and it could offer protection against future pandemics

Researchers from the Perelman School of Medicine at the University of Pennsylvania have developed a vaccine that could protect and serve as a preventative measure against future flu pandemics, reported Reuters.

The "multivalent" vaccine, which employs the same messenger ribonucleic acid (mRNA) technology pioneered by the Pfizer and Moderna SARS-CoV-2 vaccines, can protect humans against all 20 known subtypes of the influenza virus.

"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," said senior study author Scott Hensley, a professor of Microbiology at the Perelman School of Medicine, who developed the vaccine with his colleagues.

The report was published in the journal Science.

mRNA technology plays key role

Influenza viruses are known for pandemics resulting in massive death tolls. For instance, the 1918-19 Spanish flu pandemic killed tens of millions of people worldwide.

Strains of flu viruses, which can circulate among animals, can jump to humans and acquire mutations. These variations help it to spread better among humans. While we have flu vaccines, they are merely seasonal and help protect against recently circulating strains, and cannot offer protection against new pandemic strains.

When injected, the experimental vaccine produces copies of a key flu virus protein, the hemagglutinin protein, for all twenty influenza hemagglutinin subtypes—H1 through H18 for influenza A viruses and two more for influenza B viruses. 

"For a conventional vaccine, immunizing against all these subtypes would be a major challenge, but with mRNA technology, it's relatively easy," Hensley said.

The experimental vaccine doesn't provide sterilizing immunity; it does much more

When tested in mice, the mRNA elicited high levels of antibodies which effectively reacted to all 20 flu subtypes. Interestingly, the vaccine also seemed to be unaffected by previous exposures to influenza vaccines.

Unlike other vaccines, the newly-created vaccine is not expected to provide the sterilizing immunity that prevents viral infections. Instead, it elicits a memory immune response that can be "quickly recalled and adapted" to new pandemic viral strains, thereby reducing severe illness and death. 

"It would be comparable to first-generation SARS-CoV-2 mRNA vaccines, which were targeted to the original Wuhan strain of the coronavirus," Hensley said. "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."

Human trials awaited

Currently, Hensley and his colleagues are designing human trials. If the trials are successful, the vaccine can be useful for developing long-term immune memory against all influenza subtypes in people of all age groups. 

"We think this vaccine could significantly reduce the chances of ever getting a severe flu infection," Hensley said, adding that the same multivalent mRNA strategy could be used for other viruses like coronaviruses.

Professor John Oxford, a neurologist at Queen Mary University in London, who was not involved in the work, told the BBC's Radio 4 Today program that the vaccine could be ready for use the winter after next, The Guardian reported.

“I cannot emphasise enough what a breakthrough this paper is. The potential is huge, and I think sometimes we underestimate these big respiratory viruses."

Study Abstract:

Seasonal influenza vaccines offer little protection against pandemic influenza virus strains. It is difficult to create effective pre-pandemic vaccines because it is uncertain which influenza virus subtype will cause the next pandemic. In this work, we developed a nucleoside-modified messenger RNA (mRNA)–lipid nanoparticle vaccine encoding hemagglutinin antigens from all 20 known influenza A virus subtypes and influenza B virus lineages. This multivalent vaccine elicited high levels of cross-reactive and subtype-specific antibodies in mice and ferrets that reacted to all 20 encoded antigens. Vaccination-protected mice and ferrets were challenged with matched and mismatched viral strains, and this protection was at least partially dependent on antibodies. Our studies indicate that mRNA vaccines can protect against antigenically variable viruses by simultaneously inducing antibodies against multiple antigens.