So, apparently, 99.2% is the same as 0%

Well, it is if you're an antivaxxer like our old friend Meryl Dorey. Just so you don't think I'm putting words in Meryl's mouth, here's a little screenshot from the Australian Vaccination Network's blog.


The Nirvana Fallacy, also known as the Perfect World Fallacy, related to the excluded middle fallacy

What Meryl and Tom are discussing here is a paper entitled "Measles outbreak in a fully immunized secondary-school population".

It seems Meryl didn't read much beyond the title, since the actual article examines the difference between seropositive children in a fully vaccinated population (that is, those which had active antibodies against measles), and seronegative children (who didn't).

There were 74 seronegative students and 1732 seropositive students. That's about 4.3% seronegative. 14 of the seronegative children contracted measles in this outbreak. None of the seropositive students developed measles.

Ordinarily, I'd do some hokey maths here to drum in the point, but I don't have to. Liam over at SAVN did it for me

Percentage of students who *didn't* contract measles
= 1 - 14/1806
= 99.2%

Yes, that's right. The "outbreak" was confined to ~0.8% of the study population. ~19.4% of the seronegative kids got sick. 0% of the seropositive kids got sick.

There's the point, none of those who reacted as expected to the vaccine were infected. Only those who showed up as seronegative, which can happen for several reasons, were infected.

Now, let's get all speculative for a moment. Those seronegative kids could have been immune supressed, at the time of vaccination or at the time of testing. They have have been, for some other reason, incapable of reacting to the vaccine. The simplest explanation, and the one that the paper actually covers is this:

"Stratified analysis showed that the number of doses of vaccine received was the most important predictor of antibody response."
- from the paper "Measles outbreak in a fully immunized secondary-school population".

So the kids who were seronegative most likely had incomplete or insufficient vaccination, basically. This is exactly in line with the science as we understand it.

But still Meryl contends that if 100% of the population wasn't covered, then the vaccine just doesn't work.

This is, frankly, insane.

There's a fallacy called the "Perfect Solution" or "Perfect World" fallacy, also known as the "Nirvana Fallacy", closely related, but not identical to, the "Excluded Middle" fallacy (discussed with reference to Meryl here). Meryl's response to Tom is the most perfect example of this Perfect Solution Fallacy I've yet seen in the wild.

What she is saying is that 99.2% coverage, with gaps where the vaccines were incomplete or otherwise ineffective, is equivalent to no vaccine at all.

Again, don't think I'm putting words in her mouth. Read the statement above for yourself. You can even go see the statements on her blog here. She says "the vaccines simply don't prevent the disease".

Which, again, is frankly insane. Because they do, and that's what the study shows.

I think it's just icing on the cake that she then goes on to conflate "hypothesis" with "theory", channeling, not for the first time, every creationist loon ever, and then decries herd immunity, an effect which is meant to help protect those who cannot be vaccinated or do not react correctly to vaccination.

Not for the first time, I'm at something of a loss as to how to even begin to converse with someone who thinks this way. I find it difficult to believe that she's merely doing this as a deliberate, considered lie in order to shore up her position. It's too absurd. She must really believe it. All I could do was post a link to Wikipedia's article on the Nirvana Fallacy in the forlorn hope that Meryl might learn something.

I'm not holding my breath.

This is just one more reason why Meryl's nonsense must be stopped.

posted @ Tuesday, June 29, 2010 12:48 AM


Comments on this entry:

# re: So, apparently, 99.2% is the same as 0%

Left by reasonablehank at 6/29/2010 11:35 AM
You know what. I'm not very smart, and I'll tell anyone who will listen how smart I ain't. Compared to this deceitful moron, I am a fucking genius.

This is just gobsmackingly undeserved and unwarranted hubris from a mouthbreather who claims to be more knowledgeable than immunological giants. She has really outdone herself. Dunning-Kruger FTW!

# re: So, apparently, 99.2% is the same as 0%

Left by Kenny at 6/29/2010 3:01 PM
Dorey seems to alternate between psychotic delusions and outright lying. That would explain the difficulty we have in trying to have a rational debate with her.

# re: So, apparently, 99.2% is the same as 0%

Left by Sean the Blogonaut at 7/2/2010 3:05 PM
I think the best thing we can do is just keep pointing out her silliness. Those that continue to follow her after all this reported silliness are probably unreachable anyway

# done it before

Left by Andy at 7/13/2010 3:19 PM
She did something similar once before. When presented with figures showing that 88% of pertussis sufferers in a sample were vaccinated, she concluded that 88% of vaccinated kids got pertussis. Pure syllogism.
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