Riding isn't free

The problem with vaccination is that it is very vulnerable to free riding. If 99% of people get vaccinated, it is safer for your kid not to be vaccinated. It's probably safer at 95% vaccination levels. But as levels fall to, say, 85%--particularly if they are clustered among children whose parents like exotic travel--it stops being safer. It starts being deadly.

Any one person's actions will never, by themselves, tip the balance. But in aggregate, their decisions are disastrous.

That's why we create, for these situations, social and legal norms that say "No, you can't opt out." You can't not pay your taxes, even though the rest of us won't notice the added fraction of a cent this heaps on our tax burden. You can't go to the bathroom in the reservoir, even though the dilution would make your . . . er . . . contribution negligible. You don't get to dodge the draft just because you would prefer that someone else get killed defending the country.

We allow people to opt out of some of these social compacts when they are a genuine matter of conscience--you don't have to kill if you think it is morally wrong (though you still have to risk being killed by serving as a medic or in some other non-combat arm). You don't have to vaccinate your children if you're a member of a tiny cult whose children rarely leave the farm. We tolerate this largely because such genuine exceptions are few in number, and because the people who harbor them generally pay a higher price than the rest of us.

But we do not let you opt out because in your opinion, this would make you better off. The very essence of free rider problems is that every individual is better off not complying with the general practice, but the rest of us are all worse off. The only way to secure general compliance is to establish the norm that this is something you have to do even if you'd really rather not. Once you start making general exceptions, the whole system breaks down. And that system has made us all--including yes, your children--vastly better off.

Comments

Not to disagree with the "free rider" discussion, nor (in general) your comments about vaccination that prompted them but I thought I'd point out that actually there is some benefit to having less than 100% vaccination, in some cases.
I'm involved a bit with influenza response and public health and there's a hard drive here to get everyone vaccinated against the flu. Which isn't a bad idea, in part because it'll fail and you won't get _everyone_ vaccinated. Because in fact you don't really want to. Basically if they get the flu vaccine "right," then, great, people with the vaccine are protected. If they get it totally "wrong," then, well, you're no worse off ('cept for a little owie) than if you hadn;t gotten the vaccine. But there is a concept called "antigenic original sin" which describes how if they get it, well, just the right amount wrong, then the vaccine actually increases your chance of having a bad flu. That's backed up by data on ferrets (the system in which they study flu vaccination), too. So it can be useful to have less than 100% compliance.
Although me, I got the (as it turns out basically useless) shot (well, mist) this year...

Posted by Sanjay | March 25, 2008 1:43 PM

The problem with that analogy is that implicitly, it assumes that there is a benefit to the 'free riders' and germs are 'bad'.

On the contrary, there is an unknown, but potentially large cost in imposing a mono culture when you try to wipe out a particular microbe.

Vaccines can eradicate microbes that causes a particular illness. By doing so, it also means that the natural evolution between microbes and the human body has stopped in that ecological niche.

Thus, the body do not have an opportunity to develop resistance naturally to the microbe, nor do the microbe have the opportunity to evolve into a more benign form that may prove beneficial.

At the same time, the ecological niche that the microbe occupies is left vacant, wide open for another microbe with potentially more harmful effects to exploit.

Megan, with all due respect, I believe that some reading on microbes and symbiotic evolution would help you see the issue differently than this 'black and white' view of "germs".

Try: Microcosmos: Four Billion Years of Microbial Evoluton, by Lynn Margulis and Dorion Sagan or one of the more recent books like, Symbiotic Planet, etc.

To sum up Professor Margulis's argument:

We exist not as independent beings, but as a complex organ embedded in a matrix of microbes that are billions of years old. We live in a complex inter-dependent world with them where some of them can be very deadly to us (like cyanobacteria), others started out deadly, and over time, evolved into complementers that we cannot live without -e.g. mitochondria is an organism that in our distant past, was 'captured' and developed a symbiotic relationship with our cells. We cannot live without this 'infestation'.

If you take this perspective, you would have much greater difficulties with things like vaccines or antibiotics that wipe out a whole group of microbes.

Posted by D | March 25, 2008 2:00 PM

good points D ..

one of my Questions is: "Why are we giving a blanket Liability shield to these 'vaccine' manufacturers?"
http://clusty.com/search?input-form=clusty-simple&v%3Asources=webplus&query=liability+shield+for+vaccine+manufacturers

Posted by MEH | March 25, 2008 2:09 PM

D:

Wow. Dude. What if the germs were like really big, and we were really small?

Puff twice, pass to the left!

Posted by secret asian man | March 25, 2008 2:15 PM

Can we differentiate between vaccines for diseases that are easily passed (measles, mumps, small pox, etc.) and diseases that are not easily passed (hepatitis, HPV, etc.)?

I would like my kid's classmates to have their MMR vaccinations, as well as their TB shots. I don't care if they have their hepatitis shot.

Posted by Half Canadian | March 25, 2008 2:16 PM

So D, you suggest consigning millions of children to misery and death in the hopes that in a couple million years, measles will be the new mitochondria?

one of my Questions is: "Why are we giving a blanket Liability shield to these 'vaccine' manufacturers?"

So that they will make vaccines, which are a low-profit, high (legal) risk, and socially beneficial product.

Posted by Rob Lyman | March 25, 2008 2:25 PM

D, that is perhaps the stupidest argument I have ever read. You speak of some "natural immunity" process that's being subverted here without recognizing that people die from these diseases rather than develop immunity "naturally".

And Lynn Margulis is an HIV/AIDS denier who's been laughed out of scientific academia. I wouldn't be so quick to cite a lady who denies the germ theory of disease as a credible resource.

Posted by Cain | March 25, 2008 2:27 PM

@Half Canadian

Hepatitis (some forms, anyway) is fairly easily passed. Someone with hep fixes your dinner, you get hep. Happens frequently enough that every time a restaurant worker is diagnosed with it all the restaurant's patrons are urged to get the vaccine.

@MEH
The reason for the liability shield is smallpox. The best available vaccine can have nasty side effects. And while vaccinia is far preferable to variola, the side effects (scarring for life is one) would generate lawsuits.

Posted by wiredog | March 25, 2008 2:32 PM

RL,

"So that they will make vaccines, which are a low-profit, high (legal) risk, and socially beneficial product."

so the Bolt manufacturers get a Tort Pass, as well?
http://www.vfbolts.com/

Posted by MEH | March 25, 2008 2:34 PM

D's convinced me: if we wipe out the measles bug, it'll never evolve into midichlorians. There won't be a Force!

Posted by Paul Zrimsek | March 25, 2008 2:36 PM

Wow, D, I had begun to develop the sense that Megan was being too harsh on you guys, that even if she was technically right, her rhetoric was a bit extreme.

But you're really changing your argument from "I'm worried about even a small unproven threat to my children" to "please don't kill off the measles and mumps, they might turn out to be good and important?"

Posted by Geoff | March 25, 2008 2:42 PM

See what I said about dictatorial people imposing their vaccinate or else ways on the world?

Q.E.D.

Let's give them mandatory rabies shots --- though for many of them, it is probably too late.

Posted by D | March 25, 2008 2:49 PM

D's convinced me: if we wipe out the measles bug, it'll never evolve into midichlorians. There won't be a Force!

Ah, but that already happened. Not sure when, exactly, but I believe it was a long time ago.

Posted by kevin r | March 25, 2008 2:59 PM

Being bemused at the comments about Lynn Margulis, it might benefit the natives here to consider her record:

# Margulis was elected to the National Academy of Sciences in 1983 and served as Chairman of the Academy’s Space Science Board Committee on Planetary Biology and Chemical Evolution.

# She was inducted into the World Academy of Art and Science, the Russian Academy of Natural Sciences, and the American Academy of Arts and Sciences between 1995 and 1998.

# In 1998 the Library of Congress, Washington, DC, announced that it would permanently archive Dr. Margulis' papers.

# In 1999 she received the Proctor Prize for scientific achievement.

# In 1999, she was awarded the National Medal of Science by President William J. Clinton.

The odds of one of us comment writers on this blog having achieved a fraction of what Professor Margulis has in our lifetime is pretty small.

"Laughed out of "scientific academia""?

I wasn't aware that the NAS is so disrespectable that they lowered their standards to admit her!

Posted by D | March 25, 2008 3:04 PM

I don't see how vaccination can interfere with evolution the same way widespread use of antibiotics can. If we deploy antibiotics, a novel threat, bacteria will evolve to meet the new threat.

But vaccination isn't itself a threat, it merely provokes the human immune system the same way a previous infection would, and then it's the immune system which is the actual threat to the virus. But of course, the human immune system is a very natural threat to viruses, and has co-evolved with them for bazillions of years, and will continue to do so. Vaccination doesn't change the evolutionary pressure on either the viruses or humans, as they still have to fight the battle out in the old way. People whose immune systems can't defeat the virus on its own won't be helped by a vaccine. Vaccination, in essence, just jump-starts the battle, makes it start sooner, which gives a powerful advantage to the inherently slower-reacting human immune system.

To the extent this battle puts pressure on viruses to evolve towards commensality, or at least innocuity, so that they don't get suppressed, nothing changes with vaccination. Any beneficial effects of this evolution still occur.

I think D has an overly simplistic idea of what evolutionary struggle means -- for one thing, struggles that involve the death of individuals are among the least effective in advancing evolution -- and also I think he is confusing vaccines with widespread indiscriminate use of antibiotics, which is horse of an entirely different color.

Posted by Carl Pham | March 25, 2008 3:23 PM

Parents that don't vaccinate their children are not sociopaths as Megan called them in a previous post, but idiots. They are either factually wrong on dangers of vaccination (i.e. they suffer from unwarranted fear that vaccination causes autism), or they are unable to control intuitions which we all share and which are not well calibrated to handle infinitesimally small risks. But there is nothing wrong with their moral sense. It is perfectly normal, healthy, and morally justified to care about one's children very much and not to care about a stranger's child at all.
On the contrary, pathological moralists, who frame every single issue as a moral issue, are freaks.
Still, if society decides to use moral outrage to fight the problem of vaccination-dodging parents, I strongly suggest we also castigate groups and individuals that spread other superstitious beliefs about what is desirable or safe to put into a human body. For example, we should discriminate against those advocating extravagant eating habits: people that eat organic food, vegetarians and countless others indulging this sort of deviancy should be ostracized.

Posted by Jolly Inquisition | March 25, 2008 3:32 PM

I'd actually be fine with people opting out of immunization as long as this was a matter of public record.

Why shouldn't my interest, as a parent, in keeping my child free of communicable diseases supersede some other parent's interest in keeping his or her opt-out decision confidential? Death or disability is worse than a little self-consciousness.

Other parents ought to be able to make informed decisions about whether to allow their kids to play or participate in activities outside of school with the kids who are at elevated risk of carrying these diseases.

To be fair, this would have to apply to kids who can't receive vaccines for medical reasons. But I think the parents of those kids would be the first to welcome a disclosure requirement - theirs are the kids who most need to be protected from the potentially contagious. This would also allow the unvaccinated to be placed in separate classes, minimizing risk of an outbreak taking hold.

Posted by isles | March 25, 2008 3:40 PM

so the Bolt manufacturers get a Tort Pass, as well?

No, because the legal risk in making non-defective bolts is dramatically smaller, almost zero.

See what I said about dictatorial people imposing their vaccinate or else ways on the world?

No, what I see is 1) you making a weird argument that you won't defend and 2) people making the reasonable request that if you won't participate in a system designed for (and demonstrably effective at) promoting public health, then you remove yourself from society so that we need not bear the risk of your presence.

I don't care if you vaccinate or not, any more than I care if wash your hands or juggle monkey feces. None of that is my problem. Just stay away from me, that's all.

For example, we should discriminate against those advocating extravagant eating habits: people that eat organic food, vegetarians and countless others indulging this sort of deviancy should be ostracized.

The issue isn't harmless deviancy like eating kosher or vegan, it's harmful deviancy, like carrying deadly diseases. Which should be ostracized, just as surely as being a known AIDS carrier and having lots of unprotected sex.

Posted by Rob Lyman | March 25, 2008 3:50 PM

Let's give them mandatory rabies shots --- though for many of them, it is probably too late.

Is that why your foaming is increasing? I thought maybe you were just enjoying a good tap beer.

Posted by anony_mouse_ | March 25, 2008 4:35 PM

Let's give them mandatory rabies shots --- though for many of them, it is probably too late.

Is that why your foaming is increasing? I thought maybe you were just enjoying a good tap beer.

Posted by anony_mouse_ | March 25, 2008 4:36 PM

"The only way to secure general compliance is to establish the norm that this is something you have to do even if you'd really rather not."

Fur der Vaterland.

Posted by mith | March 25, 2008 4:43 PM

D, all those accolades happened before Dr. Margulis embraced HIV/AIDS denial, 9/11 truth, and Holocaust denial. I assure you her reputation is much worse off now.

Posted by Cain | March 25, 2008 4:50 PM

That would be "Fuer das Vaterland," genius.

But yes, it is certainly true that many diverse societies have found it necessary to impose controls, both legal and social, to discourage free riding and other destructive behaviors.

Posted by Rob Lyman | March 25, 2008 4:58 PM

Granting Megan's factual assumptions, I'm not seeing the argument for mandatory vaccinations here. Suppose that the expected harm from taking a vaccine is greater than the expected harm from not taking it so long as at least 90% of the population is vaccinated. Without mandatory vaccination, the vaccination rate would hover around 90% (if it got too much higher it wouldn't be worth it for people to vaccinate, while if it got too much lower it would become worth it again). What I don't see is an argument that such a situation would be worse overall than if you had mandatory 100% vaccination. In fact, society would be worse off if there was 100% vaccination, since *by stipulation* the benefits of vaccination once 90% of the population is vaccinated are less than the harms caused by the vaccine itself.

Posted by Blackadder | March 25, 2008 4:59 PM

D's post of 3:04 PM should be entered into Wikipedia as a classic example of "Appeal to Authority."

Posted by Klug | March 25, 2008 5:07 PM

To sum up Professor Margulis's argument:

We exist not as independent beings, but as a complex organ embedded in a matrix of microbes that are billions of years old. We live in a complex inter-dependent world with them where some of them can be very deadly to us (like cyanobacteria), others started out deadly, and over time, evolved into complementers that we cannot live without -e.g. mitochondria is an organism that in our distant past, was 'captured' and developed a symbiotic relationship with our cells. We cannot live without this 'infestation'.

If you take this perspective, you would have much greater difficulties with things like vaccines or antibiotics that wipe out a whole group of microbes.

D,

It is *very* easy to stand this argument on its head. The human body actually has more bacterial cells than native cells in it and we do nothing to attack them most of the time. It is only when a type of bacteria or virus shows up that exhibits pathogenic behavior that we take notice. In such circumstances we (those of us who are vaccinated, at least) use the full panoply of medical science to kill off the pathogen and only the pathogen, in so far as we are able. It seems very likely that the net effect of this will be to exert a _strong_ Darwinian pressure selecting for versions of microbes which are less pathogenic and adverse to the those that are more pathogenic. The result that I would anticipate is that antibiotics and vaccines are likely to increase the likelihood of developing symbiosis, since their net result is to select among microbes on the basis of compatibility with the human host.

Greg

Posted by Greg | March 25, 2008 6:55 PM

Blackadder:

You missed McArdle's point. The private benefit from vaccination is lower than the social benefit. The decentralized equilibrium where vaccination is set by MB_p = MC is not the same as the socially optimal equilibrium where the sum of the marginal benefits (aka MB_s) is equal to MC. Vaccination levels are higher in the latter case.

Posted by Rowz | March 26, 2008 1:13 AM

The greater good...

Posted by sam | March 26, 2008 2:21 AM

You guys need to take a step back. It's like some of you think there is a huge epidemic... Rob, whom I normally agree with, stays,

"[Not getting vaccinated] should be ostracized, just as surely as being a known AIDS carrier and having lots of unprotected sex."

I don't know how not taking steps to prevent a disease which you believe might be harmful to yourself should cause you to be shunned from society to the same extent as someone who has a disease and willfully spreads it around.

If you really believe that a parent not getting their kid vaccinated is as bad as someone who has AIDS and sleeps around we can probably end all discussion here with a "thank you very much let's agree to disagree". I'd be happy with that except for the name calling and the somewhat eerie resemblences to a severe dictatorial state with all of this "get vaccinated you evil/dumb/idiotic/sociopathic parent or else".

The irony is very heavy that parents feel free to not vaccinate under the very protection that herd immunity through vaccination has granted them.

However, it's also pretty ironic that people can bash the military while that military is out defending and sometimes dying for them... that's life. It doesn't make their opinion wholly invalid, but the hypocritical/irony of the situation does cause them to loose some "debate points"

How's this. Get your kids vaccinated. Keep their vaccines current. Keep yours current as well. That will solve the vast majority of the issues you are worrying about.

"Ah, but vaccines are no guarantee" you say, "some people will still get infected if the supply of non-vaccinated people increase."

If you're trying to force vaccination on everyone to save that 1-2% of vaccinated people who may get the disease if unvaccinated populations increase, well then you are not in much different shoes than those people who don't want to get vaccinated when they read the fine print about 1-2% of them having severe side effects. Well, except for the fact that the unvaccinated people aren't calling on using force or heavy state coercion to get other people to do what they want...

I believe that life is not fair. Accidents happen. People get sick. People die. Dibilitating disease/early death is terrible and always something most parents/people pray never happen to them.

But a lot of this thread strikes me as whining and looking for someone to blame.

My whole family got seriously sick with the stomach flu that was going around. Couldn't eat or drink anything for a couple days. You'd throw it right back up. 18mo old didn't know what was going on and was terrified. The wife was pregnant and had to go to the emergency room for an IV (1000 deductible insurance so it was expensive for us). It was terrible but at least brief. Anyway, the point is some parents were all irate and insisting that kids should be kept indoors, not brought to school, etc.

I kind of figure it's life and you're gonna get sick and you will certainly die. Hopefully it doesn't come soon.

They wanted to be mad at everyone. Kind of like how people here want to be mad. It's someone's fault. They have to be punished. Those irresponsible people are making me less safe. Calm down, step back. It's not like they have AIDs and just slept with you. They aren't walking around with ticking time bombs in their backpacks ready to explode the instant they enter a crowded room. Back of the ridiculous rhetoric and sensationalism.

Posted by sam | March 26, 2008 2:49 AM

If your child has gotten the vaccines and you believe in their efficiency then why do you care if I get mine vaccinated? If mine gets sick yours should be fine because they got vaccinated, right?

Posted by Mouseker | March 26, 2008 4:22 AM

I disagree with the ad hominem attacks against Professor Margulis. Newton was an occultist, does that invalidate calculus? Peter Deusberg, discoverer of oncogens and recipient of an NIH outstanding investigator grant by the NIH had his grant rescinded by the NIH for his assertions that HIV is not the cause of AIDS.

To be clear, I don't agree with Prof. Margulis or D's positions on this issue or Deusbergs. I just feel that science is based on testable hypotheses and repeatable experiments rather than the prounouncements of a society of priests that a person is or is not admitted into.

D doesn't seem to understand the difference between vaccines and antibiotics, as mentioned previously. Immunizing against the most virulent viruses will help those viruses evolve towards benign coexistance (or else eliminating them entirely.) Viruses that infect humans do not have 'niches,' microbes do. The analogy with microbes would be if we used phage to target only those forms of H. pylori expressing virulence factors like, say flagella. Right now, doctors only use antibiotics, which are very blunt tools.

Posted by Ryan W. | March 26, 2008 4:33 AM

Vaccinating isn't free either. Every year children die from vaccinations. I don't hear any of you commiserating over their deaths. In this country we have gone from 8 vaccines before kindergarten to 32 vaccines by age two some within hours of being born. I do not have a problem with well spaced vaccines for the few that could cause deaths if a really bad outbreak occured however the lengths we have taken it to is just rediculous. The assumption that all that will happen is just a little owie if you get vaccinated is false. There are very detrimental things in the vaccines- besides the virus. Aluminum, mercury (in everything except the infant shots including the flu shot) and a formaldayde derivative. The people that baffle me are the ones who are vegan, eat only organic or don't eat tuna for the mercury content and then go get a flu shot without checking to see what might be in it. They are so concerned with everything else that is going into their body.

Posted by Mickey | March 26, 2008 4:34 AM

As a side note, D, if you're really interested in evolving benign bacteria D you might consider Ewald's book "The Evolution of Infectious Diseases" which was used as a textbook at Miami of Ohio back when I was in school. (I didn't take the related class, but picked it up at the bookstore. It's pretty good for a textbook. )

Posted by Ryan W. | March 26, 2008 4:42 AM

I should amend my comment. I haven't read Professor Margulis so I don't know her position on this issue.

Posted by Ryan W. | March 26, 2008 5:16 AM

> I disagree with the ad hominem attacks against
> Professor Margulis. Newton was an occultist, does
> that invalidate calculus?

I'm not taking a position here, but I guess the trick would be to determine whether Margulus's writings cited in this comment thread represent her calculus or her alchemy.

And I am SO going to miss speculating on Megan's sex-life, but I try to play by the rules.

Posted by Jens Fiederer | March 26, 2008 10:11 AM

If your child has gotten the vaccines and you believe in their efficiency then why do you care if I get mine vaccinated? If mine gets sick yours should be fine because they got vaccinated, right?

Not if my children are infants, who are both too young to receive the vaccine and highly vulnerable to the diseases in question.

Posted by Emma B | March 26, 2008 10:34 AM

I don't mind not being able to opt out... but if we must go with that, than there must also be a pre-test to make sure there isn't a life threatening reaction to the shot itself. These reactions are extremely rare, and difficult to document often... but when your child's arm begins swelling up immediately after the DPT shot, and two days later they are in the ICU with unexplained brain damage, and all pathogens are accounted for by test [ie. no menengitis]... then there is very much the potential that something about that shot was wrong. I was there for that one, with a close friend whose child is the same age as mine. She's almost 14 now, and has to wear a helmet, because she is constantly trying to hit her head on things. Her mental state is of an 18month old, and always will be. Could have easily been my kid, since my kid is hyperallergic.

The odds are 1:somebignumber... unless it is YOUR kid, then the odds are 1:1. If you are going to force me to do anything, than you are willfully removing responsibility from my hand, and you must TAKE it.

I can assure you that with 2 kids not immunized, my ex and I watch very closely who is sick in school with what, and we have no compunction with keeping them home if needs be. We didn't do that for no reason, and 3 Doctors including our well known allergist back that up.

So I am wondering if all y'al who are so hot and heavy for immunizations have yours up to date? Almost all of those shots need booster every 10 yeares or so, all the way through your life, and yet no-one mentions that. Talk to your doc to see what you need boosters for. Getting measles as an adult can kill you.

Posted by SwissArmyD | March 26, 2008 10:56 AM

Just a point of clarification.

I am well aware of the difference between ATBX and Vaccines.

Stimulating the auto-immune system via a vaccine is suppose to be a nearly harmless way to protect against (name your disease).

I am raising a broader question as to what the stimulated autoimmune system also kill. In that respect, the 'blanket' nature of vaccine and ATBX action is similar.

Another question is whether stimulation of the autoimmune system in such a manner is itself a potential cause of autoimmune diseases.

There is very little solid research on the autoimmune system, which is probably one of the least understood, least documented, and least researched system in the human body.

Without any facts, I would like to speculate that there is a potential correlation link between the rise in autoimmune diseases the the type / nature / volume of stimulus it receives (natural, artificially induced ones like vaccination, etc.) and how it has changed in the last 100 years.

Posted by D | March 26, 2008 11:14 AM

Sam,

I was unclear. I did not mean to suggest that the unvaccinated should be treated like people deliberately spreading HIV (who are, after all, really criminals). I was merely trying to draw a distinction between deviancy which harms others and deviancy which harms no one by picking an extreme example.

Obviously being unvaccinated is vastly less harmful than deliberately spreading HIV.

Posted by Rob Lyman | March 26, 2008 2:45 PM

Megan = fool gold. Megan is wrong about the Iraq
war. Wrong about unvaccinated children. She
simply piss me off. Make sure your children are
unvaccinated cause vaccines are the WMD.

Posted by be-unvaccinated | March 26, 2008 3:15 PM

Without any facts, I would like to speculate that there is a potential correlation link between the rise in autoimmune diseases the the type / nature / volume of stimulus it receives (natural, artificially induced ones like vaccination, etc.) and how it has changed in the last 100 years.

How nice of you to summarize the illogical workings of your irrational mind.

Posted by Cain | March 26, 2008 6:04 PM

Why, thank you!

Virtually every great scientist I know worked that way --- they had a pretty good hunch at what the results ought to be... and then went ahead and ran experiments to prove or disprove their hunches.

Posted by D | March 26, 2008 6:30 PM

D --

Not trying to be uncivil here, but your claims of understanding would be more persuasive if you were more precise in your terms.

I think that you mean the immune system. Autoimmune is a combination of the prefix auto- meaning "self" or "same" and immune. The immune system is responsible for attacking foreign bodies within an organism. Autoimmune disorders refer to those conditions where an organism's immune system attacks the organism itself rather than a foreign body.

Posted by Brendan | March 27, 2008 3:12 PM