A randomized controlled trial of parachutes had a surprising outcome. Anti-vaxxers, take note.

One of my themes in this column over the years has been that you need to be skeptical of many of the claims out there about science and medicine. A healthy dose of skepticism can be a good thing, especially when someone is telling you something that seems surprising.

On the other hand, anti-science forces often pretend that they too are just being skeptical, or “just asking questions,” when what they’re doing is actually science denialism. Denialism is what someone is doing when the science is basically settled, but they refuse to accept it.

Let’s consider perhaps the clearest example of denialism, and the one that causes the most harm to public health: vaccine denialism. The anti-vaccine movement, which has grown alarmingly fast during the Covid-19 pandemic, insists that vaccines don’t save lives, and even more they insist that vaccines cause neurological damage. The latter claim is a favorite of Robert F. Kennedy Jr., as he’s proclaimed in multiple books and articles, and of his VP running mate Nicole Shanahan as well.

The Lancet

In defending their denialism, anti-vaxxers frequently ask this question: “where are the randomized controlled trials for vaccines?” They imply that scientists haven’t run such trials because they (the scientists) know that vaccines don’t really work.

That’s nonsense, of course. Scientists have conducted hundreds of studies, involving millions of people, showing how vaccines prevent disease and death.

But we don’t have any randomized controlled trials for childhood vaccines, and we never will, for an obvious reason: it would be deeply unethical. Let me explain.

A randomized control trial (an RCT) works like this: first, you identify a large group of people whom you want to treat, say by giving them vaccines. Then you divide them at random into two groups: the treatment group, who get the vaccine, and the control group, who get nothing. To prevent bias, you might also “blind” the subjects and experimenters so that no one knows who’s getting treated. For example, you could use shots filled with saline solution for the control group, so they think they’re getting a vaccine.

Once you’ve administered the treatment, you follow everyone for some period of time and see who does better. If the treatment group does better, then we say that the treatment worked.

Obviously, we cannot run an RCT for childhood vaccines, because withholding vaccines from children could grievously harm or even kill them. Instead, we can use data collected over time from millions of children, some of them vaccinated and some not, and measure vaccines’ effects from that. It’s not perfect, but these observational data show overwhelming evidence that vaccines for diseases including measles, mumps, rubella, polio, and smallpox are incredibly effective.

Yet anti-vaccine activists continue to call for RCTs, and they pretend that scientists who point out what I just wrote are not to be trusted.

Now to those parachutes in the title of this piece. We know that parachutes work, right? And yet where are the randomized controlled trials? Maybe we shouldn’t use parachutes until some scientists conduct that study? Hmm.

Well, if you’re thinking of skydiving and wondering about this question, you’re in luck! Because a few years ago, a group of scientists at Harvard, UCLA, and the University of Michigan ran an RCT on parachutes! And they published it, too, in the highly regarded British Medical Journal, now called BMJ.

I’m sure you’re curious about how they did this study, and how it turned out. Well, I’m going to tell you.

It was a small study: they approached 92 aircraft passengers and enrolled just 23 people. They randomized them into two groups, with 12 people wearing parachutes and 11 jumping with just an empty backpack.

What happened? Amazingly, there was no difference! Also amazingly, no one died! How could that be?

Well, reading the details of this (ahem) well-executed study, one learns that “randomized participants ... could have been at lower risk of death or major trauma because they jumped from an average altitude of 0.6 m on aircraft moving at an average of 0 km/h.”

In other words, participants did jump from a plane, but they were jumping from less than a meter off the ground and the plane wasn’t moving. A figure from the study illustrates the experiment:

So as you see, this particular RCT of parachute use didn’t prove anything. Even so, the authors note, tongue in cheek, that “Beliefs grounded in biological plausibility and expert opinion have been proven wrong by subsequent rigorous randomized evaluations. The PARACHUTE trial represents one more such historic moment.”

In case you’re wondering how on earth the BMJ would publish a study like this, I can explain that the date of publication was Christmas 2018. The BMJ has a long tradition of publishing satirical but seemingly serious articles on Christmas, and this was a particularly good one.

On the other hand, though, my larger (and serious) point is that the public shouldn’t lose trust in science. Even when science gets things wrong–and it does–it’s still the best toolkit we have for figuring out whether or not something works, or is true. The recently popular cultural trope that truth is malleable, and that each person can choose their own “facts,” is dangerous. When it comes to scientific facts, that’s just wrong.

Parachutes work, and not using them would be exceedingly risky. Vaccines aren’t quite as guaranteed as parachutes, but they come pretty close.