This could one day serve as a general preventive measure against future flu pandemics, said researchers from the University of Pennsylvania in the US. According to the study, tests in animal models showed that the vaccine dramatically reduced signs of illness and protected against death, even when the animals were exposed to strains of flu different from those used to make the vaccine. The “multipotent” vaccine, which the researchers described in a paper published in the journal Science, used the same messenger ribonucleic acid (mRNA) technology used in the Pfizer and Moderna SARS-CoV-2 vaccines, the study said. This mRNA technology that enabled these Covid-19 vaccines was pioneered at Penn, the study said. Also read | Covid-19 may increase risk of stroke in children: Study “The idea here is to have a vaccine that will give people a baseline level of immune memory to different strains of flu so that there will be far less illness and death when the next flu pandemic occurs,” said senior study author Scott Hensley. Influenza viruses periodically cause pandemics with huge death tolls. The most famous of these was the “Spanish flu” pandemic of 1918-19, which killed at least tens of millions of people around the world. Influenza viruses can circulate in birds, pigs and other animals, and pandemics can start when one of these strains jumps to humans and acquires mutations that make it better adapted to spread between people. Also read | Remdesivir could reduce mortality from Covid-19 if given early: Study Current flu vaccines are simply “seasonal” vaccines that protect against newly released strains, but are not expected to protect against new, pandemic strains. The strategy used by the Penn researchers is to vaccinate using immunogens — a type of antigen that stimulates immune responses — from all known flu subtypes in order to induce broad protection, the study said. The vaccine is not expected to provide “sterile” immunity that completely prevents viral infections. Instead, the new study showed that the vaccine induced a memory immune response that can be quickly recalled and adapted to new pandemic virus strains, significantly reducing severe illness and death from infections. “It would be comparable to the first-generation SARS-CoV-2 mRNA vaccines, which targeted the original Wuhan coronavirus strain. “Unlike later variants such as Omicron, these prototype vaccines do not completely block viral infections, but continue to provide durable protection against severe disease and death,” said Hensley. The experimental vaccine, when injected and taken up by the recipients’ cells, began to produce copies of a key influenza virus protein, the hemagglutinin protein, and for all twenty influenza hemagglutinin subtypes—H1 through H18 for influenza A viruses and two even for influenza B. viruses. “For a conventional vaccine, immunizing against all these subtypes would be a big challenge, but with mRNA technology it’s relatively easy,” Hensley said. In mice, the mRNA vaccine induced high levels of antibodies, which remained high for at least four months and reacted strongly to all 20 influenza subtypes. In addition, the vaccine appeared relatively unaffected by previous exposures to the flu virus, which can skew immune responses to conventional flu shots. The researchers observed that the antibody response in the mice was strong and broad, regardless of whether or not the animals had been exposed to the flu virus in the past. Hensley and his colleagues are currently planning human clinical trials, he said. The researchers envision that, if these trials are successful, the vaccine may be useful in inducing long-term immune memory against all subtypes of influenza in people of all age groups, including young children. “We think this vaccine could significantly reduce the chances of someone getting a serious flu,” Hensley said. In principle, he added, the same multivalent mRNA strategy can be used for other viruses with pandemic potential, including coronaviruses.
