Whatever we might each think about the decision to not vaccinate ourselves or our children, one thing is clear: vaccination is a heated topic and debates about it often result in polarization. Maybe another thing is clear too: most opinions about vaccination (for or against) are influenced more by editorials on the subject, than by data itself. Thus, here is one more editorial on the subject, albeit one that does not pass judgment on vaccinations, for or against. It is, instead, intended as a call to research, and a reminder of the scientific maxim: correlation is not causation. That goes for both sides of this debate.
On the anti-vaccination side, there are many claims made that are often based on things that the data might imply, but is far from proving. This results in many ideas that are later discredited being circulated as fact.
On the pro-vaccination side, every time there is a measles outbreak, it seems mainstream news outlets trip over themselves to implicate “the growing trend to opt out of vaccinations” as the cause (read: causation). Again, “correlation is not causation”. Here’s why…
If the measles outbreaks in California, and particularly in and around Orange County, as well as New York City are because of non-vaccinators, then why aren’t we seeing outbreaks of everything not being vaccinated for? Why just measles and why all of a sudden, when the number of people opting out of vaccinations has actually steadily dropped in the last few years – after an initial wave of people not doing it?
Non-vaccinators in NY are .1-1% of the population. In California we are talking 1.1-2%. Why aren’t we seeing increases in outbreaks in Vermont, Michigan and Oregon where the rate is over 6%? Correlation (or worse yet, public perception of correlation), is not causation: whether it’s vaccines and autism, or whether it’s a tiny number of people not vaccinating, and a few places having measles outbreaks.
What does the data show on measles in the states where opting out of vaccination trends the highest? There was an instance in Oregon last year, and one this year with a 6% rate of opting out in the state. A child in Washington County, Oregon who developed measles on an overseas trip and exposed hundreds of people in the Portland area. Add to that one case in Oregon this year where a child contracted measles from a vaccinated adult.
Shouldn’t the state be the worst off? And where are Vermont’s outbreaks at 6% non-vaccination?
Measles has been trending down, but in the past year it has spiked in the U.S. in spite of the trend of non-vaccination dropping a bit. Measles outbreaks have been happening all over the world in the past year, even and especially where there is no significant increase of anti-vaccination trends (Turkey, Vietnam, Philippines and several countries in Europe). It’s up in California which likely is accounted for by the fact that there is so much travel in California from abroad. The 2013 case in Oregon? That was a traveller too, who had been in and out of international airports before contracting the disease. Same thing with New York City where outbreaks have been happening at a rate higher than the statistical norm.
States with the highest non-vaccination rates have not seen an increase in measles outbreaks that are statistically significant. News websites like to run with headlines that will get people to share, and vent outrage. But that doesn’t make such articles a good source of scientific data.
Remember, if you take nothing else away from this: correlation is not causation. Just because you heard on the news that there are a lot of people not vaccinating their children (an exaggerated statement, to be sure), does not mean that the rise in measles globally is due to families in Utah refusing vaccinations across the board. This is all the more so when the correlation does not even overlap the places where vaccine refusal is the highest.
Do some research. Use the search field on the CDC website. Hit your local University library up and search scholarly journals and databases. The data on these issues is not hiding, but it will not deliver itself to your email inbox without a little work. When you do the research you’ll find that the facts are not quite as sensational as many headlines might have you believe. There has been a recent spike in measles. That much is clear. But it is happening all over the world and it is actually not happening in places where people are refusing vaccinations the most. Whatever your position is on vaccinations, get the facts and don’t spread assumptions made by lazy writers. Again, that goes for both sides of the vaccination issue.
(Article by M.B. David; CDC data map via Mother Jones)