I don’t have strong feelings about vaccinations. My disdain for the smug hubris of the Smart People makes me sympathetic to accusations that they understate the risks, and I do find the alleged huge increase in recommended vaccines a little unsettling. Yet my desire to be reasonable and moderate innoculates me against much of the hysteria, and I am not convinced there is non-cherry-picked causation for the recent increases in autism diagnoses, especially because as far as I understand the whole thing was literally started by a guy who was paid by lawyers to make it up so they could do lawsuits about it.
I generally stay out of the fray due to my lack of knowledge, but the other day I came across a particularly poor anti-anti-vaccination piece that displayed the very logical fallacies it attributed to its opponents, and I couldn’t help but comment. Julia Ioffe, writing in the New Republic, indignantly describes her excruciating experience with pertussis (a.k.a. “whooping cough”), blaming it all on the rising crop of folks who refuse to vaccinate their children against such things.
If you don’t think very hard, her accusation makes sense. “Since the introduction of a pertussis vaccine in 1940,” the disease “has been conquered in the developed world… Until, that is, the anti-vaccination movement really got going in the last few years.” Now cases are on the rise again!
For herd immunity to work, 95 percent of the population needs to be immunized. But the anti-vaccinators have done a good job undermining it. In 2010, for example, only 91 percent of California kindergarteners were up to date on their shots. Unsurprisingly, California had a massive pertussis outbreak.
Oh no! The anti-vaxxers are ruining the herd immunity that has kept us safe since the 1940′s! Now she has the whooping cough; “thanks a lot, anti-vaccine parents.”
But hold on just a minute. It doesn’t surprise me that places “with high concentrations of conscientious objectors” seem more likely to have outbreaks; the un-vaccinated are more likely to get the disease. But does it follow that those un-vaccinated children are also more likely to give that disease to adults like Julia Ioffe?
I don’t think it does. Other journalists have politely pointed out some logistical and technical reasons these children probably aren’t to blame. But the above link doesn’t highlight the fundamental logical flaw in Julia’s accusation that made me suspect she was wrong all along.
Julia asserts that un-vaccinated children are destroying herd immunity. This may be true, but if you’re not careful you’ll think she’s implying that this destroys immunity for everyone – as if 95% of us have been working hard to hold up this giant edifice but now that these 5% are walking way it’s coming crashing down on all of us!
Remember, herd immunity is how the vaccinated protect the small percentage who can’t be vaccinated because they’re too young or weak or whatever. If fewer people are vaccinated, it may make an outbreak more likely, and it may hurt the ones who can’t be vaccinated. But – unless I’m missing something here – it should have no effect on the 90% are still immune!
Is Julia really implying that un-vaccinated children somehow destroyed her own immunity? Of course not. She freely confesses that she was not immune: “I was vaccinated against pertussis as a child, but the vaccine wears off by adulthood, which, until recently, was rarely a problem because the disease wasn’t running rampant because of people not vaccinating their kids.”
But this makes no sense. Julia has subtly switched from claiming that the majority of the population was protecting a minority to claiming that a minority of children are no longer protecting the majority of adults. The only way to salvage her accusation that these kids gave her whooping cough is to imply that adults like her are both immune (contributing to herd immunity) and not immune (getting the disease) at the same time! But if most adults like her aren’t immune, then there wasn’t any herd immunity in the first place.
If, say, 80% of the population is walking around with worn-off pertussis vaccines, having no immunity to the disease, and some of the 20% who are children stop getting the vaccine, it makes sense that there might be marginally more favorable conditions for more outbreaks, especially if children tend to congregate more in schools and the like. But what right does one not-immune person have to criticize another not-immune person, just because they more recently joined the pack? That’s like blaming your apartment eviction on your roommate because he just stopped paying the rent, even though you haven’t been paying it for years!
A slight decrease in children getting the vaccine can only mean a very slight increase in the total non-immune population, which apparently was probably already a vast majority! How does she know that a small percentage of non-immune children are so much more to blame than the vast majority of non-immune adults all around her?
The only thing left to support Julia’s accusation is that the general resurgence in whooping cough outbreaks seems to correlate with the recent increase in the anti-vaccination movement. But now we’re back to the very correlation-causation fallacy that the anti-vaccination movement is accused of falling for in the first place. It must simply be natural to look for someone to blame, and whether it’s autism or pertussis, the attraction of the fallacy seems to play no favorites.
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