Why Is a Universal Flu Vaccine So Difficult to Develop?

as children, the elderly, and the immune compromised. More than six hundred and fifty thousand people around the world die of seasonal influenza every year, according to the World Health Organization. The seasonal flu also costs the US health care system in society in general a lot, about eleven point two billion dollars in eighteen alone. Of course, this is to say nothing about COVID nineteen, which is caused by a coronavirus, which is an hirely different virus than the multiple strains

of influenza that cause the flu. Although some symptoms of both COVID nineteen and the flu can be similar. The researchers are racing to develop the first coronavirus vaccine, though none have been successful yet. These things take time. But we've had vaccines for the flu for years, so why haven't we developed a universal flu vaccine that could stop all future iterations of the flu. The threat and impact are so great that it would surely be worth researchers time.

It has to do with the fact that influenza is incredibly cunning. We talked with Dr Greg Poland, spokesperson for the Infectious Diseases Society of America and professor of Medicine and Infectious Diseases at the Mayo Clinic in Rochester, Minnesota. He noted the trillions of new strains of the flu can develop in mere minutes. Quote, you can hardly imagine a more promiscuous virus. Fortunately, of new strains don't have genetic fitness us they can't survive. However, those that remain

can pack a pretty serious punch. Those survivors can either experience antigenic shift or antigenic drift. Let's break that down. In antigenic shift, a gnome strain of the flu morphs into a novel strain that can cause a pandemic level flu event, such as H one, N one and avian influenza. This hardly ever happens. There have been just four influenza pandemics in the last hundred years, but when it does,

it can be dire. The shift that resulted in the H one N one influenza pandemic of en sometimes called the Spanish flu, infected five hundred million people and killed fifty million around the world. This was, of course, before antibiotics were available to treat secondary bacterial infections associated with the flu. Also, vaccines were not around to prevent infection

and lesson severity. But back to shift and drift. In comparison to rare but dangerous shifts, antigenic drift happens all the time with influenza, resulting in many small changes to the virus, which makes it tricky for vaccine developers to nail even the annual flu virus squarely on the head. Poland said, so, what happens is about a quarter of a million viruses are isolated every year and genetically sequenced

to give us an idea of what's circulating. It takes six months or so to develop and distribute the flu vaccine. By that time, many of the strains have drifted to the point where they have next to no protection, meaning that one of the reasons you can still get the flu after receiving a flu vaccine is that the strain

you get may have developed after the vaccine was created. Again, these things take time, but it's worth noting here that even a mismatched vaccine is known to reduce the severity of flu symptoms and the length of the overall illness, so it's important to get the vaccine annually if you can. After all, it's better to be bedridden for three days than seven or worse, to end up in the hospital.

There are multiple roadblocks to developing a universal flu vaccine, but a number of biotech companies and academics are currently working to overcome them. Poland explained that one idea is to develop broadly neutralizing antibodies to influenza viruses that would ideally protect against every influenza strain. Let's talk a bit about how the influenza virus works. Simply put, the influenza virus is made up of a couple types of proteins

called H proteins and N proteins, plus a stock. Current vaccines attempt to teach your immune system how to hit the H and N proteins, which are what the virus uses to attach to and infect human cells. The problem is that the exact makeup of those proteins drifts all the time. By comparison, Poland explained, the stock portion is relatively invariant. So the very it has been why don't we shift how we technologically make flu vaccines to the

portion of the virus that doesn't shift and drift. Another complexity is that flu viruses only infect the outermost cells lining the respiratory tract, a part of what's called the respiratory mucosa. Flu Viruses do not replicate throughout the body, which is known as systemic replication. But we also spoke with Dr Jeffrey Taubenberger, a virologist with the National Institute

of Allergy and Infectious Diseases. He said, if you look at vaccines that provide good lifelong immunity, like measles, one of the differences there is the kind of recall you get from a systemic infection is different and much better. There's something we're not understanding about how immunity at the mucosal level sets up long term immunity. This kind of protective immunity is hard to establish. We have to come up with ways to bolster the mucosal immune responses to

give us better protection with these kinds of vaccine. So, in other words, a universal vaccine would again ideally help your immune system at the local level where the infection actually occurs, but we just don't understand enough about how that works in order to help. Once this gets worked out, it could prove helpful in the development of universal vaccines for other respiratory ailments like coronavirus. With any luck, one or more of the numerous universal flu vaccine development efforts

currently going on will pan out. A version developed by the pharmaceutical company Seek is about to enter phase three clinical trials, and Dr Taubenberger's own team is hoping to start human clinical trials on their vaccine in and don't expect a universal flu vaccine to be ready too soon, though, as it's an arduous undertaking that requires a lot of trials to get FDA approval. It's a multi step process that ensures that drugs are safe and effective. Poland explained.

Typically it takes hen or more years and it costs about a billion dollars. We should note that in case of emergency, new drugs can and have been brought through the process sooner, but it takes again, work and money. Today's episode was written by Aliya Hoyt and produced by Tyler Clang. For more in this and lots of other topics, visit how stuff works dot com. Brain Stuff is production

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