The annual flu shot has been a consistent staple
in many of our lives since the 1940s.
And for the past 80 years, the way we research and make it
has remained mostly unchanged.
Which is not really a problem.
The flu shot is estimated to save thousands of lives every year
and prevent millions of cases in the United States alone.
In other words, it’s a safe and effective way to stop the seasonal flu strain.
But what if something different emerged?
The last four pandemics before Covid-19
were brought on by an influenza virus, not a coronavirus.
And virologists agree that when it comes to the next flu pandemic,
it’s not if, but when.
But the Covid-19 pandemic has brought us new advances in vaccine technology.
And now we're closer than ever before to something new.
Something like a flu shot that protects us year after year, regardless of the strain.
Something like a universal flu vaccine.
There are a lot of different types of influenza
and researchers identify each one by looking at two proteins on the surface of the virus:
hemagglutinin and neuraminidase.
Each one has various subtypes, which can create a ton of different combinations.
And that’s just influenza A viruses.
There’s also influenza B to worry about.
A truly universal vaccine would have to cover all of these
plus anything that could potentially emerge.
SCHULTZ-CHERRY: So what makes influenza unique is its ability to change rapidly.
That's why we have to update our vaccines every year,
because as it goes through people, it changes.
The trouble is, making the vaccine takes a lot of time every year,
so in order to have a vaccine ready for flu season
researchers have to rely on a bit of guesswork.
FULLER: We have to almost predict
“What is next year's flu virus going to look like?”
Since the flu is a seasonal virus that typically appears in the colder months
scientists predict the most common strains by looking at outbreaks
in other areas of the world.
SCHULTZ-CHERRY: They'll make the decision for February
for that next September's vaccine in the northern hemisphere.
Researchers typically choose the top 4 most common strains in one hemisphere
to make the flu vaccine for the other hemisphere.
But since the virus is constantly changing,
the predictions in February aren’t always 100% accurate by September.
FULLER: The efficacy of the flu vaccine can vary
from as little as 30%, up to 70% from any one given year
simply because those predictions are not always perfect.
They're pretty good, but they're not perfect.
One solution would be to just make the vaccine closer to flu season.
But the way we currently make the flu vaccine makes that impossible.
SCHULTZ-CHERRY: Right now, our current practice takes 6 to 8 months to make the vaccine.
Scientists have used fertilized chicken eggs to grow viruses for vaccines since the 40’s.
In fact, we use so many eggs to make flu vaccines annually
that the US government actually has top secret chicken farms for this specific purpose.
But that’s a story for another time.
The point is, when a virus is prone to changing rapidly,
6 to 8 months is a ton of wasted time.
Newer vaccine technology like mRNA could dramatically shrink this timeline
because it doesn’t require growing large quantities of viruses.
As in, we could do away with the chickens and the eggs.
We’d likely be able to make a much more effective flu vaccine
because we’d be developing shots closer to the time
we actually discover the new strain.
This is one way to potentially improve the flu shot, but only up to a point.
Because making a vaccine faster doesn’t make it universal.
To do that, we have to teach our immune system to target a different part of the virus entirely.
Influenza changes fast, but not the entire virus.
Just a few pieces - specifically the top part of that one protein
called hemagglutinin, which is kind of shaped like a tulip.
SCHULTZ-CHERRY: The head of the tulip,
that's where we currently make antibodies to.
And that's the area that changes super fast,
so it’ll go from a red to a white to a yellow.
In simplest terms, our annual flu shot teaches our body
to recognize the top of that protein: the "tulip head."
Which is why one vaccine that teaches our immune system to fight off a yellow tulip
isn’t good for the next year when a red tulip shows up.
For a universal vaccine to work
it needs to teach our immune system to recognize and fight off
a part of the virus that doesn’t change as much.
Which means instead of focusing on the head
that changes year after year, from virus to virus,
many researchers have turned their attention to the stem.
FULLER: The hemagglutinin stem has been a target for universal flu vaccines
for quite some time.
KRAMMER: The problem with our immune system, is that it doesn't like to actually target the stalk.
So you basically have to find a way to convince the immune system
that it finds the stalk attractive.
There are a few ways to do that.
Some researchers have tried removing the head all together.
Others have found promise in swapping out the head multiple times
so your immune system only recognizes the stem as a threat,
and builds a stronger immune response to that.
Now, there are also other parts of the virus that don’t change as much
that researchers are looking at, which will likely be vital
for an effective universal flu vaccine as well.
FULLER: There's always the possibility that down the line
once you generate, say, a universal flu vaccine
focused on the hemagglutinin stem, that eventually the virus
will figure out a way to mutate away from that as well.
An ideal universal influenza vaccine
will not include just one conserved bit from the virus,
but multiple conserved portions from the virus.
And if we could do that,
it doesn’t really matter how fast we make the vaccine.
Because it would work year after year,
on multiple different strains of the flu.
There’s still a bit of research left to do:
trials, funding, and more.
But we’re closer than you might think.
FULLER: There are already universal flu vaccines in clinical trials.
So, we're looking at, you know, years, a few years down the line.
KRAMMER: I think 5 to 10 years is a timeframe that sounds
at least to me, reasonable.
For most people, the implications of a universal flu shot
are bigger than just not having to get a vaccine every year.
It would also make the flu vaccine more broadly available.
KRAMMER: The flu vaccines are vaccines for rich countries, right?
Low and middle income countries, specifically low income countries
don't have the infrastructure and the capacity to actually use them.
A universal flu shot that lasts for several years
could be implemented in childhood vaccination programs globally,
providing better protection for everyone from current and future outbreaks.
KRAMMER: We need to kind of put the resources into it because otherwise
we won't be prepared for the next flu pandemic either.
FULLER: So, we can do better, especially with the new technologies
like mRNA vaccines that have emerged.
There is a real opportunity to do much, much better
in terms of protecting against flu each year.