On Risk (and vaccines)

The way we perceive risk is really odd. We over-amplify some, and dismiss others. We may have a fear of flying, but are happy to drink alcohol, a known cancer-causing factor. We happily venture out into traffic with a huge number of random drivers texting, but baulk at taking a vaccine so we can travel overseas. We will climb a ladder to clean gutters at home, but not get on a boat in case it sinks.

One way of assessing risk, or possible adverse consequences of our choices, is the seriousness vs likelihood equation.

If I cross the street against the lights in peak hour, one possible adverse consequence is that I get hit by a car.

How serious, out of a score of 5, would it be if I were struck by the car? 5 out of 5?

How likely is it that I will get hit by a car? 2 out of 5?

So, multiply the first number by the second number – 5 x 2 = 10 out of a possible score of 25, which equates to 40% – a biggish risk to life and limb. Yet you see people doing it quite often.

Now, let’s apply this to taking an early release vaccine, like the Pfizer vaccine. According to the New York Times, of 44,000 people tested, 94 people suffered ill effects, like fatigue and fever. That’s 0.0021% of people tested. And it is 90% effective in preventing COVID infection. And no-one died in the trial.

So let’s apply the seriousness vs likelihood equation.

How serious would it be to get a fever or fatigue from taking the vaccine? 1 out of 5?

How likely is it that you will get fever or fatigue? 1 out of 5?

So, 1 x 1 = 1 out of 25. Even this is an exaggeration, because the likelihood is not 1, but 0.0021, which means the score would be .0021 out of 25.

For more on risk, here is a great article from La Trobe University on the likelihood of getting killed by a kangaroo and a shark!