Estimated immunization coverage with measles-containing vaccine via the World Health Organization in 2010
Anti-vaccination hysteria isn't just a set of wild conspiracy claims, it's become a big business. And like any business, the business owners aren't about to close up shop in the face of facts. Indeed, they don't view recent press on the topic as a a setback, they see it as an opportunity to pitch their debunked claims to a whole new audience. Among those long debunked claims now cropping up anew is this is one, laid to rest by Mark Chu-Carroll at
Good Math, Bad Math:
[T]here’s a paradox that some antivaccine people use in their arguments. If you look at an outbreak of an illness that we vaccinate for, you’ll frequently find that more vaccinated people become ill than unvaccinated. Therefore, they say, it’s not the fault of the unvaccinated. We’ll look at the math to see the problem with that.
Mark's post is well worth reading in its entirety. But here's the short version in non-medical terms: imagine 100,000 seat belt users and 100 non seat belt users are involved in identical rollover collisions. If a thousand seat belt users are killed and 25 non seat belt users are killed, then 97.5 percent of those killed were wearing seat belts! Does this mean buckling up is more risky? No, in fact it means the opposite. In this hypothetical illustration, non seat belt wearers were 25 times
more likely to be killed.
This same logic holds true for vaccination versus the infection attack rate. In most US outbreaks, the population exposed to the disease contains far more immunized than un-immunized people. But not all of them develop a strong immune response after being vaccinated, others become immuno-compromised due to unrelated medical conditions. So it's no surprise that in some cases, more immunized people are infected during an outbreak even though on average, they are each at far less risk individually.
Despite being corrected on this time and time again, the anti-vaccination brigades keep pitching it. A sure sign you are dealing with unscrupulous people. And they don't always stop at using bad math to claim vaccines don't work. They'll use that same bad math to imply an outbreak is caused by the vaccine itself.