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Herd Immunity Demonstration (op12no2.me)
283 points by wwkeyboard on Feb 8, 2013 | hide | past | favorite | 59 comments



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.


> Its futile to argue with them that vaccines aren't (statistically) harmful, they've already made up their minds

It's ignorance trying to defend freedom, backfitting the "facts" to their beliefs - the basis of most nutty theories. What they're really trying to defend is that government has no right dictating what one must or cannot put in their own body. But they lack the learning to be able to articulate and argue at this philosophical level (for if they had that kind of education, they'd most likely have ended up believing that society should be engineered).

It's not a good thing that these people don't vaccinate their kids and end up feeding them bleach or whatever instead, but one would be a lot better off trying to address the root causes of what makes them take an adversarial position against modern medical science, rather than wishing to paper over the symptoms with dictatorial fiats.

Also, I don't see how this is a very good simulation. As its rules are laid out, if you don't want polio, simply get vaccinated. Doesn't a large part of herd immunity have to do with even immunized people being susceptible under repeated contact with infected people?

Furthermore, it deviates from objectivity with an implicit value judgment that unvaccinated people either "cannot be vaccinated" or "are freeloaders", when it's really just individuals' utility functions. The problem with this assumption will be lost on those who'd like to engineer society, but it highlights the grave philosophical leap of the entire argument.


> What they're really trying to defend is that government has no right dictating what one must or cannot put in their own body

Talking about rights like this is useless. You have to assume some basic moral principles to proscribe who has a right to what. If I disagree with yours, then we'll just be shouting up a tree for hours.

For one, I completely disagree with the idea that the government has no right to tell people what they can or cannot put in their own body. Depending on the moral principles that a government is founded on, it very well may have that right.

> individuals' utility functions

Invoking "utlity functions" is such an appeal to naturalism. All that means is that they don't give a shit about anyone else.


Better off to disagree or debate philosophically than pretend common ground can be had, clouding the situation with dishonest arguments and fabricated 'facts'.

In most political arguments with nutty theories on one side, those on the science-backed side think they are fighting for truth against ignorance. But what they are actually advocating is an implicit philosophy of deprecating personal autonomy in favor of an engineered society. This should at least be explicit, for the benefit of all.

Analyzing utility functions obviously puts oneself first, but you overstep in trying to handwave them away as only not giving "a shit about anyone else". If we wish for systems of rules to be grounded in relation to reality (rather than taking on a self-perpetuating arbitrary life of their own), then we must consider the base case of self interest. Only after that is aligned properly can we examine emergent phenomena like societal good.


Rhetoric is not quite so black and white as you seem to want to believe. The moment you mention "engineering society" huge swaths of people will stop listening to you regardless of their inclination to agree with your fundamental argument. Most people simply do not have the patience to precisely understand any argument with the accuracy that an expert in the field feels is necessary.

Note that I am not saying you have to play fast and loose with facts or fabricate anything, but simply: phrasing matters.


Everything you believe is based on the idea that everyone has relatively equal agency in their lives.

But that's a load of horseshit.

And that's the only thing I have to say to you.


> For one, I completely disagree with the idea that the government has no right to tell people what they can or cannot put in their own body. Depending on the moral principles that a government is founded on, it very well may have that right.

So you are saying, a government of the kind that you approve of has the right to demand that people be vaccinated, and one of the kind that you disapprove of does not.

This does not compute, the outcome is the same, as is the science.


No, that's not what I was saying. If the moral maxim of a government is to ensure maximum stability and health for its citizens, then of course it has the right to dictate what substances people must or must not put in their bodies and it would have the right to do so quite invasively.

If the moral maxim is individual liberty at all costs, then it doesn't.

I would imagine that most government are formed on much more complex maxims than either of those two simple ones. The US government is ostensibly founded with the purpose of the Preamble of the Constitution in mind (though of course this has no bearing on actual legal rights granted, then again, we're not really debating laws in this discussion):

> We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.

That's quite a few overarching principles and I'm sure you could imagine situations in which attending to one concept would impede or cause the regression of another. Now of course, we could be talking about different governments and establishing different guiding principles for each, but I was just bringing up this one as an example.


>But they lack the learning to be able to articulate and argue at this philosophical level (for if they had that kind of education, they'd most likely have ended up believing that society should be engineered).

Citation needed. I have "that kind of education" and I surely don't believe that "society should be engineered".


What they're trying to defend is that they like the social contract, except when they don't.


The only thing this seems to leave out is the individual "will not be vaccinated"'s culpability in the spread of the disease to one of the "cannot be vaccinated"s.

Manslaughter charges as part of the utility function then?

Two or more people living within each others influence is an engineered society. The only question is what does the engineering. "If you choose not to decide, you still have made a choice".


Aren’t people free to decide not to vaccinate?

Calling that a morally reprehensible decision (which it is) is not in any way problematic and has nothing to do with the government at all.


But if/when they become ill, they then become a burden on society. They consume more healthcare, impact/infect friends, family, and strangers, and are potentially quarantined by the local health officials.

More about the authority to quarantine someone: http://www.ncsl.org/issues-research/health/state-quarantine-...


More so than the obese? The smokers? the drug users? People who sit all day and never move?

I think they're pretty nutty myself. But if you're going to call them a burden on society's resources, you have to open up the argument to be inclusive of everyone who fits that bill.


What’s your solution to this?

This is direct action for fear of direct consequences, not something controversial at all. By refusing to go into quarantine, you are potentially hurting other people’s freedom. One or the other has to give.


IMO, this is where personal responsibility has to trump personal freedom. If you're sick, you have a duty to isolate yourself.


>As its rules are laid out, if you don't want polio, simply get vaccinated.

Yeah you missed the point. I quote:

Herd immunity is important because there are number of people who cannot be vaccinated for health or age reasons - herd immunity effecting an indirect and statistically safe space for them.


From what I read from herd immunity you second to last paragraph is incorrect or it used a definition of herd immunity that I did not encountered yet?

Can you point some material providing this information?


Yes, except for vaccines that target virus(es) that are part of a group in which there may be only a 15-59% chance that it will protect outside of the laboratory. Per the Lancet and per the CDC, this is the case with seasonal flu vaccines. And, you have a small percentage actually die or have ongoing health problems because of problems with the vaccine.

References:

"The Lancet medical journal, the study found the seasonal flu jab, available free to seniors, is only 59 per cent effective...": http://www.theaustralian.com.au/news/health-science/seasonal...

"Influenza vaccine would be estimated to be only 15% effective": http://www.cdc.gov/flu/professionals/vaccination/effectivene...

http://www.cdc.gov/flu/protect/keyfacts.htm#side-effects


59% may be perfectly adequate to provide herd immunity, passing the phase transition threshold. It depends on a lot more detail than "59%".


Measles cases are at "an 18 year high" in the UK because people don't immunise. (http://www.independent.co.uk/news/uk/home-news/measles-cases...)


You should be aware that there are different reasons why people oppose vaccination. There's the group that claims it is unhealthy, but there also are groups that oppose vaccination for religious reasons (http://en.wikipedia.org/wiki/Vaccine_controversies#Religion). You will need a religious argument to convince members of those groups (well, some members. There are indications that some of them have their children vaccinated in secret, but keep that hidden from their church members because of peer pressure)


Do remember that the current flu vaccine (as an example) has an efficacy rate of less than 65%. So even if 100% of the population were vaccinated, herd immunity would not be possible.

Herd immunity requires about 75% + efficacy of the vaccines (and assuming 100% of the target population is vaccinated), from what I can understand (it varies based on how the disease being vaccinated against, is spread).

There are vaccines being sold and marketed, that have efficacy rates as low as 35%.


Is efficacy binary? A partially protected person could spread less and recover more quickly than someone who isn't protected. I'm not sure enough of the math to know whether 100% of people being 65% protected works the same as 65% of the people being 100% protected, but it might not be.


Mostly binary. The flu vaccine protects ~99% against some strains and 0% against others.


It may not be, but I think that is the way it is modeled.


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

My sister wants an app to help explain to clients who don't understand cash flow problems. "How can I be broke? I make more money than I spend!" (Not this month, you didn't)

I'll see what I can do with Cocos 2D. It'll be like my Wa-Tor inspired A-Life programs from middle school.

EDIT: BTW, this applet runs just fine on my iPad as it is.


Can you confirm that? You can run an applet inside your ipad? You mean a Java application?


The demo in the link is an HTML5 canvas element animated with Javascript.


Yes, and it runs just fine on both the iPad and my iPhone 5. Sorry for the confusing terminology. I remember the time everyone would do that kind of thing in a Java applet.


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.


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?


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.


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


Precisely my point. The vaccination had no critical effect on any graph and the decreased incidents of polio following suggest a natural progression of technology and disease knowledge and awareness. The drugs that existed before the vaccine were not in wide scale production and play no relevant part in considering the impact of polio on the public.


I don't have the data to definitively suggest that the epidemics could have been eradicated by methods other than vaccine. Its entirely possible that they could.

But while we're talking about vaccines and personal freedoms and all that yap, do lets remember that some of those other methods they were using to combat these epidemics back then were forced quarantines on pain of arrest, interstate travel restrictions, and the closing of public buildings like pools, libraries and schools.


That's a graph of the death rate from polio, not of polio incidence. I don't know this for sure, but think it likely that incidence stayed the same while death rates went down.

http://en.wikipedia.org/wiki/History_of_poliomyelitis#Iron_l...:

"even with an iron lung the fatality rate for patients with bulbar polio exceeded 90% [...] Positive pressure ventilators reduced mortality in bulbar patients from 90% to 20%. In the Copenhagen epidemic of 1952, large numbers of patients were ventilated by hand"

That 1952 epidemic is better described at http://jap.physiology.org/content/99/2/424.full, about a 1952 epidemic in Copenhagen:

"The bold solution was to manually ventilate the patients by squeezing a rubber bag attached to a tracheostomy tube inserted through an incision just below the larynx. [...] the mortality rate is said to have dropped from ∼90% to ∼25% as a result of this heroic intervention."


What is the source of that graph? Why does it only cover a period of about 16 years?


I've found multiple graphs that show many different timelines. This page has a very similar graph at the very bottom that gives a reference.

https://wiki.ecdc.europa.eu/fem/w/fem/line-graphs.aspx


That's also a death rate chart, it doesn't take into account how many people got infected and then had to deal with the crippling after effects of a polio infection such as permanent muscle paralysis, disability and deformity.

The death rate for soldiers has likewise been lowered due to the great advances in medicine, but many of these survivors are now living (thankfully) and facing a new set of problems like missing limbs and other body parts.


Epidemics are noisy... This graph doesn't reflect that. Consider this. A ton of people get polio. Then we have herd immunity for 25 years until the percentage of the population that hasn't been exposed rises. Then we have a huge epidemic again. Since the vaccine, we haven't seen a large epidemic except in populations without high vaccination rates.


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...


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...

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

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


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.


Ring vaccination?


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."


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.


Interesting. Like what fire-fighters do with bushfires: remove the fuel to contain the outbreak.


It's a process where you contain outbreaks by identifying them and vaccinating everyone who might come in contact with an infected person. You create a "ring" of vaccinated people around the infected, which prevents the infection from spreading.


Intentionally creating a pocket of herd immunity around an outbreak.


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


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.


Nicely done.

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


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.


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.


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.


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


it would be interesting to see how this effects herd immunity


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.




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