You're probably not going to win an argument with an over zealous anti vaxxer. You're definitely not going to win an argument or change anyone's mind if you don't know what you're talking about. Here's a primer.
Vaccines Cause Autism
Them: Vaccines give kids autism
You: No, they don't.
In 1998, Andrew Wakefield published a scientific article widely believed to show a connection between the Measles, Mumps, and Rubella (MMR) vaccine and several medical conditions, most famously autism. That's the oft told story. It's also utter malarkey because the study said no such thing. The interpretation of the published article concludes: "We identified associated gastrointestinal disease and developmental regression in a group of previously normal children, which was generally associated in time with possible environmental triggers."
"Where does autism come into play here," you rightfully wonder? Although no association between the MMR vaccine and autism was actually proven in the paper, Wakefield talked about it in the press conference about the paper. His comments received a great deal of media attention – this was a medical article, in a top tier medical journal, saying that we are endangering our kids! Vaccine rates dropped, rates of preventable infectious disease went up, the world cowered in fear that injecting particles of dead bacteria and viruses would give children autism. Emotional parents gave emotional interviews. So what if the interpretation of the published article says nothing about autism and the vaccines. "Did you hear what that guy said at the press conference?!"
Click that link to the article. See how in big red letters plastered across it is the word "RETRACTED." Oh, was it retracted! Wakefield, that rapscallion, had manipulated data for the study and it was fully retracted in 2010. I'd like to give a shout out to the unsung hero in all of this, reporter Brian Deer, who found actual evidence (as opposed to, say, the stuff that Wakefield made up) that Wakefield had been paid by lawyers seeking evidence to use against vaccine manufacturers. Additionally, that several of the parents involved in the study were litigants in the suit. That is one hell of a conflict of interest.
The study was retracted and Wakefield's license was revoked. The rates of vaccination never recovered from the hit taken when Wakefield took the stage. Here, have some links to a few articles establishing no connection between vaccines and autism.
Them: It's the thimerasol that does it
You: Thimerosal isn't actually a component in most vaccines anymore, but that's irrelevant because it was never a problem in the first place.
Thimerasol is an organomercury compound used as a preservative in vaccines. Although there is zero evidence linking it to autism, some are convinced it's a causative factor. This point is also irrelevant, because it's no longer used in routine childhood vaccines in the US.
Them: FINE. The components of vaccines don't cause autism or a sudden and unexplained change in my child. But the vaccine schedule does. It's too many, too fast.
You: I would ask you to point me to some kind of study showing this, but none exists.
This is an argument popular among adults who finally caved to the idea that there is no research that the MMR vaccine causes autism.
The current US immunization schedule is timed to protect children when they are most at risk. No scientific data has been found showing that vaccine schedules pose any risk to children. You know what spreading vaccines over multiple visits does? Inflicts additional pain on your child and makes them hate doctors. It leaves them vulnerable to serious infectious diseases as infants until you, in all your wisdom, decide it's time to protect your children. It increases health care costs. It accomplishes nothing.
Them: Other kids are vaccinated, I don't need to vaccinate mine.
You: You are a terribly selfish human being. Also, you're wrong.
Me: I have gone temporarily blind with white hot rage. You should not be allowed to interact with people. You should be forced to pay roughly $177,000 per unvaccinated child set loose upon this world (that was the approximate cost associated with the measles out break in San Diego in 2008).
The term "herd immunity" is used here to reflect the idea that if a certain number of people in the population are vaccinated, the chance of contracting an infection can drop down to almost zero. If the pathogen was introduced to the community, it would not be able to get a foothold because most people would be resistant to it. Herd immunity also indirectly protects children too young or sick to be vaccinated and susceptible adults. When enough people in a community decide not to vaccinate their children, you begin to see outbreaks of preventable disease.
Anti-vaccination parents are deciding that they can benefit from the indirect protection granted by herd immunity. This is an example of a wildly unethical and selfish behavior that, for some reason, people are not completely humiliated and ashamed to admit to. Here is an actual quote I heard from a parent who didn't want to vaccinate their child: "How many kids would really die if they got measles? 1:100? Is it worth risking my child getting autism for that one kid? I mean, it's sad for their parents but…"
Most of the parents making the decision about vaccines didn't grow up with friends paralyzed from polio or lose someone to diphtheria. It's easy to discount the need for vaccines when these diseases seem too distant to be a threat. It's possible that if these diseases feel like real threats, parents will change their minds and start vaccinating their children. That works out well, because we're seeing more outbreaks everyday — there's a solid chance we'll all get to witness an epidemic of a previously eradicated disease right here in 21st century America!
Rates of Autism
Them: Rates of autism are going up over time. It's because we give too many vaccines.
You: That's true. But that doesn't mean vaccines are to blame.
Legitimate scientific organizations like the CDC place rates of autism at 1:68, a significant increase from the 1:150 we saw in 2000. Why?
I can tell you, based on all we discussed above, that the recent increase in rates of autism is probably not related to vaccines we have been using for decades. It could be connected to an unknown environmental factor. Many experts believe that an increased awareness of autism spectrum disorders (ASD) has led to increased rate of diagnosis. Both parents and doctors may be noticing symptoms that had been overlooked before. Children who in the past may have been diagnosed with mental retardation or considered socially awkward are instead being identified as on the spectrum. ASD now incorporates far more than autism. You can't expand the spectrum and expect the numbers to stay constant.
Them: The need for vaccines is a conspiracy - pharmaceutical companies are in cahoots with doctors.
You: You can't be serious.
If people want to see a conspiracy, they're going to see a conspiracy. Don't argue with these people. Instead, change the subject to something about UFOs or the grassy knoll.
Please keep in mind that there are several valid reasons for not vaccinating children (allergies, immunodeficiencies, etc). Please be respectful of that. But the people spouting the above absurdities? Crush them in an argument, even if you can't make them change their minds. Even if you come to a stale mate, those people eavesdropping on your argument? The ones who haven't quite made up their minds as to whether they want to vaccinate their children? Those are the people you're trying to win over.
Combating ignorance with knowledge is the only possible way to move us forward. I have to believe that's true, because otherwise we really are all screwed.
Working Title: God I really hate some people
ETA: Commeter Neisseria did a great summary of a depressing study that shows educating anti-vaxx parents doesn't necessarily work. That's (often) true. As I said, you're probably not going to change their minds. What are you left with? The people eavesdropping and those trying to make a decision. Arguing with people running full tilt on the power of their ignorant convictions is a losing battle. Not everyone is there yet.