This week’s hot Internet story was Julia Ioffe writing in The New Republic about her whooping cough. [Mention on DK FP; Volokh Conspiracy; Discover] As she points out, whooping cough (also known as pertussis) had almost disappeared in the United States, but cases are on the rise. One reason is that a growing number of Americans are refusing to vaccinate their children.
As expected by anyone who has ever seen vaccination discussed on the Internet, Ioffe’s comments section rapidly filled with anti-vaccine cranks. Some approach from the right, with claims of personal autonomy that trump even the libertarian night-watchman state's power of quarantine. Others come from a narcissistic pseudo-Green belief that their Superman immune systems, fortified with expensive supplements, can take on all those pesky germs. How dare we ordinary people complain that in reality they are free-riding on our assuming the non-zero (albeit small) risks of vaccination! [Note: autism is not one of these risks.]
Either way the denialists have a major statistical problem: the near-eradication of several diseases in the course of vaccination campaigns. Flailing attempts to solve this problem include: Big Pharma has persuaded doctors to reclassify paralytic polio as something else; sanitation and hygiene improved; the disease rates were going down before vaccines; and people who are vaccinated still get sick (no one, of course, denied this).
No pseudo-scientific campaign is complete without pseudo-statistical nonsense, and in following the antivax links I encountered some real doozies. A few of them are generalizable to bad statistical reasoning in general, so for the details and maybe a good laugh, follow below the cronut.
1. Easy Warmup — What’s wrong here?
This is strong evidence showing that the Polio vaccine is not responsible for the decline and should negate the belief and statement that the Polio vaccine demonstrates vaccine success. Below, see research that reflects what it stated above.
2. Missing Data Are Data They Don't Want You To See The anti-vaxers pick the narrative back up in 1961. We shall see why the 1950s got disappeared.
In 1977, Dr Jonas Salk, who developed the first polio vaccine, testified along with other scientists that mass inoculation against polio was the cause of most polio cases throughout the USA since 1961 [Emphasis added].
4. You Say Morbidity, I Say Mortality, Let’s Call the While Thing Off Another frequently-cited antivax web site explains “there is no credible scientific evidence that the vaccine caused polio to disappear.” This claim’s original source is a parenting book by eccentric pediatrician Dr. Robert Mendelsohn, who, despite the importance he gave to diet over medicine, died aged 62 from a heart attack complicated by diabetes. Pro-vaccine Dr. Spock lived to 94. For some reason, Dr. Mendelsohn did not accompany his statement that polio declined in European countries that did not vaccinate as fast those that did with any data or even a source citation. The web site, however, continues with this remarkable chart.
5. At the Last Gasp, Botch the Math Given the evidence that the number of cases of these diseases declined drastically after the introduction of vaccines, antivaxers tend to change the subject. Their reasoning skills, however, don’t improve.
Table 1 at the end of Dr Witt’s document shows the percent of cases in the vaccinated, and it as follows: 86% age 2-7, 86% age 8-12, 62% age 13-18, 81% age 2-18. So now you know who gets more pertussis. It is not the unvaccinated.
Take 1000 kids. 95% vax rate. Make the vaccine 80% effective. That says the susceptible population is 50 unvaccinated kids and 190 unsuccessfully vaccinated kids. That means that, on average, the cohort of sick kids will be 190/240=79% vaccinated! In other words, the very fact that the number of unvaxed kids is minuscule makes it more likely that those kids who do get sick come from unsuccessful vaccinations.
For vaccines that are more effective, even this seeming paradox does not occur. In the recent measles outbreak in the New York Ultra-Orthodox Jewish community, every victim was unvaccinated, either too young or by refusal!
The percentage to look at is not the number of vaccinated children in the sick group, but the comparative likelihood that an unvaccinated child gets sick. Dr. Witt’s complete study is available free online. The very same Table 1 shows that unvaccinated or undervaccinated children were, with 99% significance, twice as likely to get sick. Indeed, that was the purpose of Table 1; see the screenshot for yourself. Vaccines work.
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