With the amount of controversy out there about vaccines, you could forgive some families for thinking it's a big risk to vaccinate their kids. But as awesome as we humans are, our perception of risk is notoriously unreliable. Scared of flying? You've got a 1 in 11 million chance of dying in a plane crash, whereas you've got about a 1 in 5,000 chance of dying in a car accident, but do you even think twice about stepping into your car every morning? And as Henry Reich points out in the latest episode of MinuteEarth, 9 percent of Americans have an actual fear of zombies, and they don't even exist. "So it's not hard to see how lots of scary talk about vaccines can be paralysing," he says.

But here's the thing - the risk associated with vaccines is real, but it's very, very small. And they prevent far riskier treatments such as medicine and surgery, which doctors only resort to if it's absolutely necessary. To put it in perspective, if you're going under general anaesthetic for surgery, you've got a 1 in 19,600 chance of waking up during surgery - with the rates as high as 1 in 670 for certain procedures. Nasty side effects from chemotherapy are almost universal, and even something as seemingly innocuous as Viagra can cause at least one unwanted side effect in half its users.

But none of these treatments get nearly the amount of negative press that the vaccine for measles, mumps and rubella gets, and you know what the most common side effect is? A harmless, low-grade fever. That occurs in 1 in 6 patients, and 1 in every 20 patients experience a minor rash. If you're really unlucky, you'll experience a severe allergic reaction, but we're talking a 1 in 1,000,000 chance. Yep, one in a million.

"In fact, in your lifetime, you're about three times more likely to be killed by an errant firework, 80 times more likely to be struck by lightning than to have a severe reaction to the MMR vaccine," says Henry.

So are the World Health Organisation (WHO), the US Centres for Disease Control (CDC), and your doctor lying when they call the MMR vaccine "safe"? Nope, because when you weigh up the associated risks and benefits, they are overwhelmingly on the side of "This will probably hurt for a second so you never have to experience the actual pain and suffering caused by a serious disease."

But there is one major downside of vaccines, and it's not what you think. It's not the side effects that we should be worried about, but the reality that because vaccines are so effective at eradicating infectious diseases, we've forgotten how horrendous they are. We've forgotten what the real risks actually look like. Watch MinuteEarth above to see what it takes to change this attitude, and why we really should just listen to the science in the first place.