
Herd Immunity Demonstration - wwkeyboard
http://op12no2.me/toys/herd/index.php?scenario=intro
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noonespecial
This is excellent. I'm going to add it to my little bag of arguments for those
times I encounter anti-vaccine types.

Its futile to argue with them that vaccines aren't (statistically) harmful,
they've already made up their minds. So I agree. All medical interventions are
harmful in _some_ cases. Instead, I simply ask them what makes them special
that they should be allowed to avoid the small risk of the vaccine as opposed
to everyone else. After all, if no one was vaccinated, there would be polio
epidemics, which most will concede are worse than the risks posed by vaccines.

Asking them why they are exempt from preventing polio while everyone else must
shoulder the burden often turns a mindless stream of conspiracy jargon into an
almost stunned pause.

I'd pay for an app that runs this simulation just to make this point sharper.

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toolz
<http://www.vaclib.org/intro/present/polio.gif>

I'm not anti-vaccine, but I am anti-sensational unsubstantiated claims, such
as without the polio vaccine there would be epidemics.

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JumpCrisscross
That's a graph of the death rate from polio, not the number of deaths from
polio. Polio drugs existed before the polio vaccine (and still exist today).
Similarly, one could graph U.S. mortality rates over the 20th century, observe
its generally smooth downward slope, and conclude that nothing done after 1980
had any effect on anything. Or graph world mortality rates over the second
millenium and similarly write off the 20th century. Maybe this is just a case
for logarithms?

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tedunangst
Comparing with other graphs, it is number of deaths. Unless measles had a 600%
death rate. <http://www.vaclib.org/intro/present/index.htm#8>

But as I alluded to in my other comment, the range of years for each disease
is different. Almost as if each graph were cherry zoomed, as it were.

Also worth mentioning, the decline in typhoid and scarlet fever wouldn't have
anything to do with the development of antibiotics and chlorination of the
public water supply, would they? Thinking that because some bacterial diseases
had non-vaccine cures, therefore all diseases can be similarly cured is...
what it is.

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JumpCrisscross
Rates, particularly in epidemiology, are often rescaled as deaths per thousand
or hundred thousand.

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JumpCrisscross
I found Vynnycky & White's _An Introduction to Infectious Disease Modelling_
[1] fantastically interesting to go through. I know games are the traditional
"fun" way to learn a programming language, but simulating a Resident Evil or
28 Days Later apocalypse is, for me, far more interesting :).

[1] [http://www.amazon.com/An-Introduction-Infectious-Disease-
Mod...](http://www.amazon.com/An-Introduction-Infectious-Disease-
Modelling/dp/0198565763/ref=sr_1_1?ie=UTF8&qid=1360366453&sr=8-1&keywords=infectious+disease+modelling)

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marcelsalathe
This is a cool visual demonstration of the concept.

The concept of herd immunity, and how it breaks down, especially due to
personal opinions, is my main research interest. I've published a couple of
papers over the years, for those who are interested (all are open access):

The effect of opinion clustering on disease outbreaks
[http://rsif.royalsocietypublishing.org/content/5/29/1505.ful...](http://rsif.royalsocietypublishing.org/content/5/29/1505.full.pdf+html)

Assessing Vaccination Sentiments with Online Social Media: Implications for
Infectious Disease Dynamics and Control
[http://www.ploscompbiol.org/article/info:doi/10.1371/journal...](http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1002199)

Complex Social Contagion Makes Networks More Vulnerable to Disease Outbreaks
<http://arxiv.org/abs/1211.0518>

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danielford
These simulations are wonderful. I'll be showing some of them to my
microbiology class later this semester when I discuss vaccines.

I wish there was a simulation for ring vaccination though. It would be a nice
visual aid for explaining how smallpox was eradicated.

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oconnor0
Ring vaccination?

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ghshephard
From: <http://en.wikipedia.org/wiki/Smallpox>

"In the early 1950s an estimated 50 million cases of smallpox occurred in the
world each year.[5] To eradicate smallpox, each outbreak had to be stopped
from spreading, by isolation of cases and vaccination of everyone who lived
close by. This process is known as "ring vaccination". The key to this
strategy was monitoring of cases in a community (known as surveillance) and
containment."

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mark_integerdsv
Reading this reminded me of an anti AIDS campaign we have here in South
Africa. I can't bring to mind the catch-phrase but the gist of it is that one
HIV free generation could stop the virus forever.

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csense
It would be interesting to run the freeloader situation with 1% freeloaders,
2% freeloaders, ..., 99% freeloaders, each 1000 times, and plot the
probability that more than half the population are eventually infected as a
function of the number of freeloaders.

I'm thinking the graph will show a sharp spike at a critical transition
probability because it's a similar model to percolation [1].

In fact I may write my own simulation for this.

[1] <http://en.wikipedia.org/wiki/Percolation_threshold>

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SoftwareMaven
My wife works as a pediatric nurse. It is sad to see the impacts as parents
make idiotic decisions and more and more kids are gettings sick with
potentially life-threatening diseases. I think we have dropped below the level
of herd immunity.

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ChuckMcM
Nicely done.

Now if they could add freeloader tipping point as a function of population
mobility it would really drive the point home.

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fnordfnordfnord
As pointed out by a commenter at the site, the simulation doesn't address
mortality rates of disease outbreaks. Nor does it address the risks associated
with vaccination. If taken seriously, it's likely to leave some with mistaken
perceptions.

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tomkinstinch
As an aside, red and green are poor color choices for things like this where
color perception is necessary for discrimination. I'm colorblind and cannot
differentiate the "infected" squares from the green ones. Black would be a
better choice than red. In fact, everything could be grayscale.

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TazeTSchnitzel
OT: Surprisingly, I was able to use this in the Opera Mini mobile proxy
browser. The fact the server preserved page state and streamed page updates
meant it actually worked surprisingly well, albeit with a low framerate.

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billpg
Remember, some of those green squares don't just turn blue, they die.

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zekenie
it would be interesting to see how this effects herd immunity

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sesqu
It doesn't. A dead person is effectively immune, that is "recovered". Popular
modifications that do affect the model include temporary immunity and new
births.

