A universal flu vaccine -- one that provides immunity against every strain of the influenza virus for multiple years -- is the holy grail of flu research. It would be a medical breakthrough on the order of penicillin, with the potential to save hundreds of thousands of lives every year. And scientists just got one crucial step closer to making it a reality.
Two separate groups of scientists published papers this week demonstrating that a new type of flu vaccine can provide protection against multiple strains of the disease, rather than just one. Though a truly universal flu vaccine that could be given to humans remains years away, infectious disease experts hailed the new findings as a major breakthrough.
"These are very good papers. There are no problems with them," Dr. Peter Palese, a renowned flu expert at Mount Sinai Hospital in New York, told The Huffington Post. "What we need to do now is put [these vaccines] in humans and see if they work. That's the only question at this point."
One group of researchers, whose findings were published in the journal Nature Medicine, tested the new type of vaccine on mice and ferrets, while the other group, which published its paper in Science, tested it on monkeys. Both teams found that the vaccine increased the test subjects' immunity against both the H1N1 flu type, often called "swine flu," and the H5N1 type, or "bird flu." Until now, all flu vaccines have only been able to protect against one specific strain of flu.
Even if it's determined that the new vaccine type can work in humans, years of clinical trials will be needed before such vaccines could come to market. But if the research pans out, experts believe that within the decade, we could have a vaccine that protects against all strains of influenza for years on end.
“The goal would be to try to make it so that you don't have to get immunized every year -- but maybe once every five or 10 years. That would be a major step forward.”
American virologists Jonas Salk (1914-1995) and Thomas Francis (1900-1969) developed the first-ever flu vaccines in 1938. Every vaccine developed since then has operated on the same basic principle: The vaccines lead the human immune system to produce antibodies that attach to the end of the flu virus's hemagglutinin, the part that the virus uses to access our cells. The antibodies prevent the virus from successfully invading the cells and causing disease.
But the reason vaccines can protect against only a single strain of the flu is that the ends of the hemagglutinin are structured differently in each strain.
Flu shots generally contain three or four different types of vaccines, so they can offer immunity to the handful of strains that scientists predict will be most common in a given season. But the flu virus can change its genetic makeup so quickly that the ends of its hemagglutinin change completely from year to year, which is why a vaccine given one year confers little to no immunity from a subsequent year's flu strains. Hence the need to get a flu shot every fall.
But the scientists who wrote the two papers published this week took an entirely different approach. Instead of targeting the invasive ends of the hemagglutinin, they targeted the "stems," which connect the ends to the rest of the virus. Since the structure of these stems doesn't vary much between different strains of the flu, an antibody that attacks the stem should defuse a wide variety of strains.
Scientists never even thought to develop vaccines aiming at the hemagglutinin stems until recently, because it only became clear a few years ago that humans produced antibodies that targeted the stems.
That's partially because humans don't produce very many of these antibodies. And it's still unclear whether any vaccine could spur our immune systems to produce enough stem-targeted antibodies to fight off flu strains.
Even if a vaccine can trigger production of a sufficient quantity of stem-targeted antibodies, no one knows how long the body will do so after vaccination, so we have no idea how long any immunity conferred by such flu shots would last.
"In a perfect world, it would last for life," said Dr. Ian Wilson of the Scripps Research Institute in La Jolla, California, who is one of the authors of the Science paper. "But we have no idea how long it will last for the moment. The goal would be to try to make it so that you don't have to get immunized every year -- but maybe once every five or 10 years. That would be a major step forward."
Still, one concern is that flu viruses could start to vary the structures of their stems more widely than they currently do, mitigating the advantage of this new type of vaccine.
"It's a constant arms race with all of these viruses," Wilson said. "Basically, the immune system can neutralize the virus that's infected with, then the virus escapes, and the immune system attacks the new virus … This is a constant process with all viruses."
Only more research -- including human trials -- will be able to answer these questions.
Dr. Barney Graham of the National Institute of Health, who is one of the authors of the Nature Medicine paper, told HuffPost that the two teams were aware of one another's work. The researchers who published the Science paper, he said, "made [the vaccine] in a different way, and used different materials and such, but they ended up showing very similar results. So both papers complemented each other and supported each other."
"This is a proof of concept that puts us on a path toward a universal vaccine," Graham continued. "It's not that we have something that's going to be in a bottle next year. I don't want people to get that impression. But it is exciting, because it does put us on this path that could lead to something."