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Health and medicine
Course: Health and medicine > Unit 13
Lesson 4: Influenza- What is the flu?
- Catching and spreading the flu
- When flu viruses attack!
- Three types of flu
- Naming the flu: H-something, N-something
- Testing for the flu
- Antiviral drugs for the flu
- Genetic shift in flu
- Flu vaccine efficacy
- Flu shift and drift
- Two flu vaccines (TIV and LAIV)
- Flu vaccine risks and benefits
- Making flu vaccine each year
- 5 common flu vaccine excuses
- Vaccines and the autism myth - part 1
- Vaccines and the autism myth - part 2
- Flu surveillance
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Flu vaccine risks and benefits
Learn about some of the common and uncommon risks and benefits associated with the flu vaccine! Rishi is a pediatric infectious disease physician and works at Khan Academy.
These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Rishi Desai.
Want to join the conversation?
- so the immunized persons in the "herd" actually have an invisible force field around them? I assumed the virus would still enter their body, but their immune system would be ready to defeat it. I thought this would mean that the immunized persons could still potentially carry the virus to an unimmunized person. Could you please correct me.(3 votes)
- Herd immunity actually is referring to the likelihood of transmission of the disease. When a large percentage of a population is vaccinated or immunized against a disease the chance of encountering an individual with the disease is much lower.
If an individual with the disease encounters, lets say five other people, and all of these individuals are vaccinated or immunized then the disease transmission is prevented. When the ability of a virus to transmit from person to person is reduced to a specific level it is considered a "Herd Immunity".
In short, the individuals without immunizations or vaccinations are still able to get the disease but the likelihood of the disease being transmitted to them is drastically reduced. Hope this helps!(10 votes)
- so an immunized person cannot carry or transmit the Flu virus?(2 votes)
- You can still give it to someone, though it's far less likely. If you touch something that has the virus on it and you shake someone's hand before the virus is killed, you can transfer the virus to them. But you won't transmit it via coughing and sneezing, like you would if you had the flu (except maybe for a brief period time after exposure, if you happen to cough or sneeze for some other reason). The virus can only live on your hands (or a surface) for so long, and it can be killed by simply washing them, so it's pretty unlikely that you'd make someone sick that way. With the live virus, if you develop a runny nose, there might be a small amount of virus in the mucus, but that's not very likely to make anyone sick, either.
That's my understanding of it, anyway. The vaccine only causes your immune system to kill the virus when it's inside your body, so any viruses that it can't get to are unaffected. If you get exposed to the virus, there may also be a short period of time between exposure and immune response where, as I said, you might be able to transmit it if you happen to sneeze. I'm not sure how likely it is for a vaccinated person to transmit the flu, but it should theoretically be possible for those reasons.(2 votes)
- if you are negating any links between vaccine and other issues, what study are you using to make your estimate regarding attributable rate? the mathematical equation for attributable rate includes a population exposed (vaccinated in this case) to a population unexposed (un vaccinated). Again, please cite your reference for these statements. cant find any like that on pub med(4 votes)
- athe talks about the Vaccine Efficacy being 60 to 70% 3:00
Does that mean for both types, the TIV and the LAIV?
Could one have more Efficacy than the other one?(2 votes)- See this other video on Flu Vaccine Efficacy:
http://www.khanacademy.org/science/healthcare-and-medicine/influenza/v/flu-vaccine-efficacy(5 votes)
- just curious can vaccines actually kill people or do more harm than good, if so how and why?(0 votes)
- When vaccines first started being made, there were several incidences where they were contaminated, either by live (not weakened) viruses for the disease they were vaccinating against, or by some sort of bacteria or fungus. A lot of people died from these mistakes, but because of them, the companies who make the vaccines now know to make sure they're handled properly and made exactly right. Every now and then, a batch will get contaminated (a batch of steroid shots--not a vaccine, but still relevant--was contaminated with fungal meningitis last year), but it usually gets noticed and recalled pretty quickly, and the people who received it are monitored so they can get treatment quickly if they do get sick.
Even in the early days of vaccination, when quite a few people died from mistakes, it was still a great deal smaller than the number of people who died from the actual disease. Vaccinations save tens of thousands of lives per year. As terrible as it is that people have died or suffered serious complications as a result of vaccinations, this is incredibly rare and represents barely a tiny fraction of the number of people who would die from these illnesses otherwise.(6 votes)
- I've been writing a program to demonstrate Herd Immunity on Khan Academy. I wanted to use the flu as a model, but I have been having trouble finding out things like;
- what is the chance of infection from a single contact?
- how is the chance influenced by the person being vaccinated?
- how many interactions are expected, and how does this vary based on population density / lifestyle / etc?
- are some vaccinated people rendered immune, or is the best you can hope for a high resistance? How do I model this?
- is there a chance of natural immunity, say from previous infections or interactions?
The program can be found here (still a work in progress, be kind!):
https://www.khanacademy.org/cs/spin-off-of-herd-immunity-ver-4/5384941264175104
I would love any help/advice on this.(2 votes)- Vaccines are never 100% Sometimes it is effective sometimes it is not, it depends on whether it elicits an adequate immune response from the body. There are many variables to determining whether someone will get sick when exposed. One major variable is viral load. How many viral particles did the person inhale? 10 or even 50 probably won't make someone sick. But inhaling 1000 viral particles probably would (if they haven't been vaccinated) In a vaccinated person it might take 100,000 particles instead, but that could still be enough to overwhelm the immune system. Flu viruses constantly mutate so a natural immunity is unlikely for most people. However there is always a small subset of the population with a natural immunity to almost any concievable pathogen.(2 votes)
- Thanks Dr. Desai! I appreciate the numbers that you included for how often the "uncommon" risks and benefits are observed. I was interested to put them in a form that made them easier to compare so that I could see where the numbers lead.
First the benefits:
~200,000 hospitalizations resulting from contracting the flu as a % = 200,000/315,000,000 = .063%
<= 49,000 deaths resulting from contracting the flu as a % = .015%
Now the risks (ignoring GBS since it seems like an anomaly):
1/1,000 Febrile Seizures resulting from flu vaccine as a % = .1%
As a number, this .1% of 22,900,000 children under 5 in the U.S. in 2011 translates to 22,900 children each year getting Febrile Seizures which result from flu vaccines (my estimate is based on http://www.childstats.gov/americaschildren/tables/pop1.asp?popup=true).
Regarding children under 5 years old from 2010-2011, the CDC reported 60 deaths (http://gis.cdc.gov/GRASP/Fluview/PedFluDeath.html see bottom left chart)and 20,000 hospitalizations (http://www.cdc.gov/flu/protect/children.htm). This translates to a death rate of .0002% and a hospitalization rate of .087%.
Based on this much, it seems that the "uncommon" risks and benefits are very much that: uncommon. An interesting observation is that if all children under 5 got the flu vaccine, we would expect to see 22,900 (.1% * 22,900,000) children having Febrile Seizures. This means that more children would be having seizures than are currently hospitalized by the flu. Is my math right?(2 votes) - If it's dead virus then who is responsible for the runny nose?
Is it dead virus or attenuated ?(1 vote)- First, he specifically says it isn't dead, its weakened. The runny nose is part of the body's defense response to the presence of a virus, dead or weakened.(2 votes)
- Should an adult that has never contracted any Flu Virus there whole life worry more about getting vaccinated then someone who gets it often?(2 votes)
- if you regularly meet with a) young children, b) elderly, and or c) immuno-compromised persons then you can help them be safer by getting vaccinated(1 vote)
- Where do you get your Vaccine Effectiveness stats from? On the CDC website where they track it, the effectiveness changes every year, and lately has been trending down as of last year to 23% http://www.cdc.gov/flu/professionals/vaccination/effectiveness-studies.htm.
How can you state that the effectiveness is between 60-70% when every year a new vaccine is made for a different strain? It is too short of a period of time to make an extremely effective vaccine unless the strain does not change or manufacturers/WHO get lucky.(1 vote)
Video transcript
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.