Imagine a single dose of vaccine that prepares your body against every known strain of flu — the so-called universal flu vaccine that scientists have been trying to create for decades.
A new study describes successful animal trials of such a vaccine, offering hope that the country could be protected from future flu pandemics. Like the Covid vaccine made by Pfizer-BioNTech and Moderna, the experimental flu vaccine is based on mRNA.
It’s in its early stages – tested only on mice and ferrets – but the vaccine provides important evidence that a single shot can be used against an entire family of viruses. If the vaccine is successful in humans, the approach could be used against other virus families, perhaps including coronaviruses.
The vaccine will not replace annual flu shots but will provide a shield against serious illness and death from potential pandemic threats.
“There’s really a need for a new flu vaccine to protect against the pandemic threats out there,” said Scott Hensley, an immunologist at the University of Pennsylvania who led the study.
“If there’s a new flu pandemic tomorrow, if we had a vaccine like this that was widely used before that pandemic, then we might not have to shut everything down,” he said. He and his colleagues vaccine description last week in the journal Science.
By age 5, most children have had multiple flu infections and have gained some immunity — but only against the strains they encounter.
Dr Hensley said: “Our childhood exposure to influenza forms a lasting immune memory that we can recall later as adults. But “we are living the rest of our lives dependent on random chance of whatever we were infected with as children.”
Current flu vaccines protect against seasonal flu but will provide little protection against a new strain that could emerge as a pandemic threat. For example, during the 2009 H1N1 swine flu pandemic, conventional vaccines provided little protection against the virus. But older adults who were exposed to H1N1 strains as children develop only mild symptoms.
Scientists have long been trying to create a vaccine that could help children deal with every strain of flu they may encounter later in life. But the researchers were constrained by technical barriers and by the diversity of influenza viruses.
Collectively, there are 20 subtypes of influenza, each representing thousands of viruses. Current vaccines can target up to four subgroups. But the experimental vaccine contains all 20 vaccines, and it will be produced more quickly.
The researchers found that the vaccine produced high levels of antibodies to all 20 flu subtypes in ferrets and mice — a finding that some experts call surprising and promising.
If the vaccine works similarly in humans, “we will have broader coverage of influenza viruses – not only those that are circulating, but those that could be spilled from animal reservoir and could cause the next pandemic,” said Alyson Kelvin, a researcher. vaccine expert at the University of Saskatchewan in Canada, said.
Packing 20 targets into one vaccine has one drawback: The antibody levels in the test animals were lower than when they were vaccinated against each individual strain. But levels are still high enough to be effective against the flu.
Because a new pandemic influenza strain might differ from the 20 targets included in the experimental vaccine, the researchers also tested the vaccine against viruses that weren’t a perfect match. The vaccine still offers strong protection, suggesting that it will at least prevent serious illness, if not infection, from a new pandemic influenza virus.
This phenomenon is similar to that of the current Covid vaccine: Although the latest Omicron variants are very different from the ancestral virus, the original vaccine did not prevent infection, it continued to occur. Continuing to help protect most people from serious illness.
Dr. Kelvin said this quality could be a particular advantage of mRNA vaccines. Regular flu vaccines only target the specific viruses they are designed to fight. But mRNA vaccines seem to produce antibodies that protect the body against more viruses than those included.
Experts note several important caveats and questions that must be answered before a vaccine becomes a viable candidate.
The animals in the study built up defenses against all 20 strains of influenza equally. Richard J. Webby, an influenza virus expert at St. Jude of Memphis, said: “These animals have never had the flu before.
Dr Webby notes that such a complete lack of immunity against the flu is only true of very young children. Older adults are exposed to many different strains of the virus throughout their lives, and it is not clear whether their immune response to the universal vaccine is fairly uniform.
“The evidence for the pudding would be what happens when it enters humans and how entering a pre-immune population distorts the response to it,” said Dr Webby.
Designing universal vaccines for different age groups, if needed, will be a challenge. It will be important to see how long such protection from a vaccine lasts, some experts say.
“The biggest issue with global flu is what do you need to target and you can keep getting that vaccine,” said Ted Ross, Director of Global Vaccine Development at the Cleveland Clinic. in how long. “If you have to keep updating it, it may not increase the advantage of the way we manufacture vaccines today.”
The next step of the vaccine will be testing in monkeys and humans. But proving its effectiveness can be a challenge. “How do you evaluate and adjust a vaccine when their target is out of circulation and so you can’t really demonstrate effectiveness?” Dr. Kelvin said.
Perhaps the vaccine could be tested in sporadic outbreaks or in poultry farmers at risk of contracting avian influenza viruses, she said: “Those are the questions I ask. I think we need to respond before the next pandemic.”
