Why Is a Universal Flu Vaccine So Difficult to Develop?

Today's flu vaccines can absolutely prevent or lessen an influenza infection, but they have to be taken yearly and don't always work. Learn why -- and what researchers are doing about it -- in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of iHeart Radio, Hey
brain Stuff, Lauren vogelbam here. Your annual flu shot protects
you from some types of influenza, usually the ones that
got people sick the year before, but if a new
strain of flu shows up, the shot may not work
for it. That's why holy grail of medicine is to

(00:23):
create a universal flu vaccine, and a universal flu vaccine
can't come soon enough, especially for particularly vulnerable populations such
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.

(00:44):
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

(01:05):
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

(01:26):
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

(01:48):
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.

(02:14):
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

(02:34):
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

(02:55):
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.

(03:15):
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

(03:36):
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.

(03:58):
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

(04:21):
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

(04:42):
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

(05:04):
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

(05:25):
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

(05:46):
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

(06:09):
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

(06:33):
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

(06:54):
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.

(07:17):
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
of iHeart Radio or more podcasts. My heart Radio visit
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