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Flu vaccine risks and benefits | Infectious diseases | Health & Medicine | Khan Academy

September 7, 2019


So a lot of people are
trying to decide about whether flu vaccine is for them. They want to know,
what are the risks and what are the benefits
of getting the flu vaccine? So I’m going to write up
here the risks and benefits. We’re going to go through
them kind of systematically, and hopefully by the end,
you’ll have a nice little table you can look at to take a
look at kind of both sides, side by side. So let’s start with some
of the common issues. What are some of
the common things we know are going to be
a risk with the vaccine? Well, when you walk
in to get a vaccine, you kind of know, if it’s
an injectable vaccine, that the injection is not
going to be pain-free. I mean, most injections are
going to hurt a little bit. And so this, actually, for
some people is not a big deal. But for others, like
me, it is a big deal. You know, I always remember,
people would tell me, oh, it doesn’t hurt that much. And I would feel like they
lied to me, because I always felt like it did hurt. And so I always got
some arm soreness. And it’s not pleasant. And that was one
of the main reasons I often kind of dragged my
feet about getting the vaccine. I thought, well, you know, do
I really want to go in today and get an injection in my arm? And the one that causes arm
soreness, the one that we inject, is the dead vaccine. I just want to
make it very clear. And we call it TIV. That’s the name of the vaccine. So if you don’t like getting
an injection in the arm, if you’re like me, then you
can also get the other vaccine. There’s this other
vaccine out there. And it’s going to
cause, potentially, a little bit of a runny nose. This is something
that some people get. I’ve actually always
opted for this one whenever it was available. It’s the live vaccine. And it’s not for everybody. Some people are
actually not going to be able to get this one. Now, in all the
years I’ve had it, I’ve actually never
had a runny nose, although I know a lot of people
say that they’ve had that. So these are the common
issues, or the common risks you take when you
get a vaccine, right? Now, another thing
is that they often are thought to cause the
flu, but they actually do not cause flu. This is a huge misconception. So I want to make it very clear. Something that is dead–
a virus that is dead– is not going to
cause flu for sure. So that one’s kind of obvious. But even this weak virus,
this weakened virus that’s in the vaccine, is also
not going to cause the flu. It causes symptoms that
sometimes are unpleasant, like a runny nose, usually,
but it doesn’t cause the flu. So what about the other side? What are the benefits,
the common benefits that we know you can
get from the vaccine? What are the reasons
we even take vaccine? Well, you want to stay healthy. You don’t want to get flu. And that’s the whole
point behind this. And this is kind of how
I qualify it to myself. I think, well, you
know, would I even be OK with getting an
injection in the arm? Probably, yeah, because I
know that in terms of pain, that might hurt a
little bit, but being on your back in bed for three
or four days, sometimes more, because of the
flu, that’s awful. And that’s real suffering. So I would definitely
opt for getting a vaccine over getting the flu. Now, you know, we
measure something called vaccine efficacy– kind
of the ability of the vaccine to prevent us from getting ill. And the vaccine efficacy of
this vaccine is not perfect. That’s something we
have to remember, right? It’s not 100%. It’s actually, we think,
somewhere between 60% and 70%. So if I’m going to draw a little
force field, a purple force field, showing that I’m
protected from the flu, I’ve got to actually
also show a couple of little holes
in my force field to say that it’s not a
perfect bit of protection. But it’s pretty good, and
that’s the whole point, right? So those are the common
benefits that you can expect. Now, let me draw a
little bit more space up here so I can continue with
this risk/benefit analysis. What are some uncommon things? What are some
uncommon, more rare events that you
may have heard of, people sometimes talk
about, with the vaccine. And there are a couple. There are two that kind of
jump to mind I’ll talk about. One of them is called
Guillain-Barre. Kind of a tough
word to even spell. But it’s basically
a nerve disease that causes problems– actually,
instead of disease, let me write syndrome. It’s basically going to
cause problems with muscles. And so you get muscle weakness. So Guillain-Barre Syndrome–
sometimes we call this GBS, so you might see GBS– is
essentially a nerve disease. And the reason we even
talk about Guillain-Barre– you might think,
well, what do nerves have to do with the flu vaccine? Well, it turned out,
interestingly enough, that back in 1976– so we’ve
been giving flu vaccine for a long time– back in
1976, it was observed– and this was unbelievable how
they were able to find this, but they found one extra case–
one extra case, approximately, of Guillain-Barre So one extra
case of Guillain-Barre Syndrome among 100,000 individuals
that were vaccinated. So they said, well,
that’s interesting. We didn’t expect this person
to have Guillain-Barre. And there seems to be an
association with the vaccine. So as a result of finding this
kind of risk back in 1976, we’ve been looking ever since. So in the last
30, 40 years we’ve been kind of looking every
year, and people are kind of encouraged to report if
they have Guillain-Barre And we have not seen a real
association between the flu vaccine and Guillain-Barre
ever since this year. But we still continue to look. And people still talk
about Guillain-Barre and ask questions about it. So that’s why I
wanted to bring it up. Now, the other thing
that actually, I think, people talk about maybe
even more commonly than Guillain-Barre,
is febrile seizures. And if you’ve ever
seen one, these things are pretty frightening. These are basically a seizure
in a young child after a fever. And I completely
understand why parents would be worried if they
ever see one like this. And you wouldn’t want to see one
in your own child, of course. But the risk of febrile
seizures with flu vaccine is also quite low. So you usually see about
one case among, let’s say, about 1,000 vaccinated kids. So it’s also pretty low. And here, the reassuring
part– the thing that is probably most
helpful for parents to know– is that if your child
has a febrile seizure, they almost always get better
quickly and completely. There’s no kind of
long-term brain damage that you get from febrile
seizures– nothing like that. So it is frightening
to look at and to see. It’s scary, no doubt about it. But the kids do recover
really, really well. And they don’t have
any long-term problems. So let’s jump to the other side. What are some of the
uncommon benefits? And, actually, I’m
saying uncommon. I should even put it in– well,
I was going to put in quotes. I guess I can do that. Because actually,
some of these benefits are more common than
you would think. And so we talk about
hospitalizations, right? And deaths. And people think,
well, you know, it’s not very common to have
to go to the hospital or to die from flu, right? And actually– I wrote “die”
when I meant “deaths”– and actually, there are
many, many hospitalizations and deaths happening
each year in the US. These are US numbers, right? But you can kind of get
a sense for these numbers and project them to your
own setting, wherever you may be living. In the US, we see thousands
and thousands of deaths, year after year, related to the flu. This is based on
some research that’s been done over
the last 30 years. And hospitalizations as well. We see 200,000 per year. So these are not
uncommon things, really. And what are people dying of? What is the cause of
death in hospitalizations? Well, it’s things like
pneumonia or bronchitis. These are pretty
common ailments, and they can land
you in the hospital. And sadly, they can actually
land you in the grave because they’re so serious. And also, things like asthma. Asthma attacks can be
triggered by the flu. And if you’re a
parent, you can really appreciate things
like ear infections. And you can get sinus
infections related to the flu. And more generally,
bacterial infections. So a lot of bacteria
like to wait for the flu to infect, and then right
afterwards they kind of jump in and cause infections as well. Let me just spell this out
just to clear up any confusion. So these are actually fairly
serious issues, right? These are not trivial. And they’re much, much more
common than a lot of people think about– all
these things, right? And so when you’re comparing
them side by side, on the one side– on the
benefits side– you’re avoiding hospitalization
and death from fairly common things. And on the other side, you have
truly uncommon things– things that happened and were
noticed a long time ago, or people recover
completely and fully from. So between the two
sides, again, I would say that, based
on this information, the benefits win
out over the risks. So now let me just bring
up a little bit more space. And I’m going to get
into one final issue, and this is around something
that is really troubling. This is around myths, things
that simply are not true. And there are a lot of them,
actually, around flu vaccine. There are a lot of myths. And over the years, I’ve noticed
that there’s been a shift. So a long time ago, I would
always hear the same question. People would say,
hey, isn’t it true that the flu vaccine
can cause autism? Because I heard that on
the internet, or my mom forwarded me an
email about that. And that is definitely
and completely not true. So this is not a real thing. That does not happen. And then later, over time,
I started hearing, well, maybe it’s not the vaccine. Maybe it’s something
inside the vaccine. Maybe it’s this thing
called thimerosal. Or maybe something within
thimerosal, because thimerosal is actually a preservative. Maybe it’s this mercury
within thimerosal. And maybe that causes autism. That was kind of the new thing,
I would say, a few years ago. And that also has been kind of
proven, and shown in studies, not to be the case. So what do people actually
talk about nowadays? What’s the new
myth on the block? There’s always a new
myth on the block. And the new one is maybe,
just generally speaking, too many vaccines– and
nowadays, it’s funny, I don’t even hear
about autism so much– they say maybe too many
vaccines are just bad. And literally, that’s
exactly what people will say. They’ll say, I don’t
want another vaccine, because I’ve just
heard it’s bad. And maybe more generally,
they might say, bad for the immune system. So this is kind of the most
common new rumor on the block, or myth on the block. And so I want to just
kind of go through these– and we’ll go through these
in other videos one by one and talk about why
they’re not true, but it’s very clear,
based on research, that these are not true. But now, separate
from myths, what’s one final argument
on the benefits side? Well, it’s called herd immunity. And you may have heard
this term before– you may have heard
about herd immunity. Kind of hard to say
a few times out loud. But herd immunity is
basically the idea– let me try to sketch it
out for you– that you have a community, right? You’ve got all these people. Each white circle
is another person, and they’re all living
together in a community. And some of these
people are going to be what we call vulnerable. So let’s say that this is
a three-month-old beautiful little baby. So a three-month-old baby. And this baby is too young
to get the flu vaccine. But of course, Mom and
Dad are right here. So Mom and Dad get the vaccine. And maybe Uncle Joe
gets the vaccine, and Auntie Smith
gets the vaccine, and Grandma, Grandpa
get the vaccine. And cousins who are also around
the baby get the vaccine. And so you get the idea. Basically, all the
people around this baby are going to get the vaccine. And now a stranger
comes to visit. This is a person
from another city. They come to visit. And what everyone
doesn’t know is that this person’s
actually sick. And they come to a dinner. And they start coughing. And of course, they’re
spreading germs. Well, what this family
has done is that they’ve created this nice
little zone, it’s called “the safe zone,”
between anyone that’s sick and the baby. So these germs are not going
to be able to kind of penetrate this barrier because too
many people are vaccinated, and so these germs can’t
cause enough infections to get to this baby. So this baby is really
protected over here. So that’s kind of
the goal, is you want to keep vulnerable
members of our community– including babies and the
elderly and other folks– you want to keep them safe. And the best way
to keep them safe is by getting
vaccinated and creating that protection for yourself.

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