Since signing up for Mike Adams’s newsletter the other week (to get this full post from him), I’ve been getting a daily load of “Health Ranger” woo in my mailbox. I’ve been ignoring most of it, but I thought it worth deconstructing Wednesday’s rather dangerous piece of Adams misinformation (some redundancy there, admittedly). Adams thinks he has found something that shows vaccination against the mumps means you are more likely to get the mumps than if you forego the vaccine. He’s wrong,of course (as I will show below). All it shows is that Adams doesn't understand his own numbers.

First, check out Adams’s post, Mumps outbreak spreads among people who got vaccinated against mumps:

To hear the vaccine pushers say it, all the recent outbreaks of mumps and measles are caused by too few people seeking out vaccinations. It's all those "non-vaccinated people" who are a danger to society, they say, because they can spread disease. Reality tells a different story, however: It is the vaccinated people who are causing these outbreaks and spreading disease! Just this week, an outbreak of mumps among more than 1,000 people in New Jersey and New York has raised alarm among infectious disease authorities. The outbreak itself is not unusual, though. What's unusual is that the health authorities slipped up and admitted that most of the people infected with mumps had already been vaccinated against mumps. In Ocean County, New Jersey, county spokeswoman Leslie Terjesen told CNN that 77 percent of those who caught mumps had already been vaccinated against mumps. [Bold in original.]

What he is saying is that more vaccinated kids (77%) than non vaccinated, got the mumps, therefore you are more likely to get the mumps if you are vaccinated. He is wrong, because he is asking the wrong question. He is asking, “did more vaccinated kids get the mumps than non-vaccinated?” (Answer – yes. 77% v 23%.) The question he should be asking is, “if you are vaccinated, are you more or less likely to get the mumps?” A subtly different question. The answer to that question is “less” – you are less likely to get the mumps if you are vaccinated. In fact, if you are vaccinated you are one seventh as likely to get the disease, compared with the unvaccinated. As I will now demonstrate.

Adams is quoting this CNN report as the source for his “77%” New Jersey figure, so that’s what I will go with. From this CNN report, we know that:

The mumps outbreak also spread to Ocean County, New Jersey, where 159 confirmed cases have been diagnosed since September, county spokeswoman Leslie Terjesen told CNN. [...] Of the New Jersey cases, 77 percent were vaccinated, Terjesen said.

Now, if you look at this CDC table you will see that 96.1% of New Jersey kindergarten pupils are fully vaccinated against the mumps. I’ll round this down to 96%. That means, the number of vaccinated children is 24 times (96 divided by 4) the number of unvaccinated. Remember that figure.

Now consider this: if in New Jersey, 159 children got the mumps, and 77% of those were vaccinated, then that means that 122 (159 x 77%) vaccinated children got the mumps, while 37 unvaccinated children got the mumps. Hold those numbers too.

Suppose 1,270* children were exposed to the mumps. We know that 96% of these (on average) were vaccinated – that’s 1219 vaccinated children. 51 children (4%) were unvaccinated.

I’ll remind you again that 159 children in New Jersey were infected, and that 122 of these (the infamous 77%) were vaccinated. So, what is the answer to my question, if you are vaccinated, are you more or less likely to get the mumps? Some elementary arithmetic:

Vaccinated and got the mumps

122 / 1219 = 10%

Unvaccinated and got the mumps

37 / 51 = 73%

Answer – if your child is unvaccinated, he or she is seven times more likely to get the mumps.

So how do we explain the 77% figure? Easy: more vaccinated children got the mumps because there were more vaccinated children to start with. 24 times more as many, to be precise. If the vaccine were completely useless and offered zero protection against the mumps, we would expect 24 times the number of infected children to be vaccinated, compared with unvaccinated. (Since both groups would be infected equally, but the vaccinated group is 24 times larger.) The fact that we only get about three times (77/23) the number of vaccinated children with the disease, demonstrates how effective the vaccine actually is.

Ironically, the higher the vaccination rates, the higher is the proportion of vaccinated children out of the total who will get the disease. For example, suppose we have 100% vaccination rates. Obviously this would never happen in reality, but just suppose for argument's sake that the vaccination rate is 100%. Also suppose the vaccine is not 100% effective (which does reflect reality - the mumps vaccine is only about 90% effective). What percentage of infected children will be vaccinated? Obviously 100%, since there are zero unvaccinated children in our hypothetical. Now imagine instead that 0% of children are vaccinated. What percentage of infected children now will be vaccinated? Obviously 0%. So the higher the vaccination rates, the higher the proportion of vaccinated children out of the total who get the disease. Which is, of course irrelevant. The relevant fact is that with higher vaccination rates, fewer children overall will get the disease.

I’ve tried to show this in a table:

Group Total % of Total Infected Group % of Infected Infected % of Group Vaccinated 1,219 96% 122

77% 10% Un-vaccinated 51 4% 37

23% 73% Total 1,270 100% 159

100%

Adams is looking at the percentage of each group (vaccinated v. unvaccinated) that are infected. This error is what causes him to write nonsense like this:

Vaccines may actually increase your risk of disease. Notice that far more vaccinated children were stricken with mumps than non-vaccinated children?

But, as I’ve shown, that’s irrelevant. The relevant information is the percentage in each group that will become infected. And seven times the number of unvaccinated children, compared with unvaccinated, get the mumps. While I understand that this 77% figure can be confusing for people who aren't used to thinking about these things, Mike Adams does this for a living and so he has no excuse. And it's not as if this is a new phenomenon - I remember discussing this exact same thing eight or nine years ago on the JREF forum. The answers have been out there for a while, so why does Mike Adams still promote these kinds of false conclusions?

(* I chose the 1,270 figure because according to the CDC the effectiveness of MMR against mumps is approximately 90% after two doses – which matches the calculated 10% infection rate with 1,270 children. The ratio (1:7) works out exactly the same though, no matter what number of children you assume.)