One Question Quiz
Toby Morris for The Spinoff
Toby Morris for The Spinoff

ScienceFebruary 20, 2021

Siouxsie Wiles & Toby Morris: The Covid vaccine is a delicious great big slice of cheese

Toby Morris for The Spinoff
Toby Morris for The Spinoff

Today the NZ vaccination programme begins in earnest, with the first doses provided to border workers. Why is that so important? Siouxsie and Toby spell it out, cheesily.

With the arrival of the Pfizer/BioNTech vaccine into New Zealand and the start of the roll-out to our border and isolation/quarantine workers and their families, we now have a new slice of Swiss cheese to add to our Covid-19 defences. 

Back in October, Toby Morris and I explained the concept of the “Swiss cheese model of system accidents”, which is widely used in medicine, engineering, and the aviation industry and is good way of thinking about our Covid-19 defences. The idea dates back over 30 years and comes from James Reason, a psychology professor at the University of Manchester. Reason was trying to shift people from blaming individuals for failures within complex systems. Instead, he thought a better culture would be one which tried to understand how and why the failure had happened to prevent it from happening again.

In Reason’s model, every complex system should have layers of barriers and safeguards. The layers are needed because no single barrier or safeguard is guaranteed to work all of the time. They each have “holes” in them. Like some types of Swiss cheese – like Emmental! The important idea behind the model is that a hole in one layer of defence isn’t necessarily a disaster if there are lots of other layers to fall back on. Hence having multiple slices of Swiss cheese. Then it’s only when all the holes line up that the defences are breached. 

As a quick aside, I have to give a shoutout to Jan Davies, a professor of anaesthesiology, perioperative and pain medicine at the Cumming School of Medicine and the University of Calgary. Jan emailed to tell me the origin of the Swiss cheese name. It was the late Dr Rob Lee, a psychologist in the Royal Australian Air Force who came up with it. Davies explained that in 1990 Lee visited Calgary and “greeted me waving a copy of Jim’s paper, excitedly saying that I must read it!” Davies had been working with Lee to develop a method of investigating anaesthetic and other healthcare-related deaths. She went on to work with Reason and they published the first application of the Swiss cheese model in healthcare. Lee was made an Officer in the General Division of the Order of Australia in the 2012 Queen’s Birthday Honours for “distinguished service to the aviation industry, to the development of air safety and accident investigation standards, and to national and international professional associations”. He died in 2018.

A new slice of Swiss cheese!

Here in New Zealand, we are using a multitude of slices of “cheese” to minimise the chances of Covid-19 getting into the country and limiting its spread within the community if it does. We have border controls and putting travellers into a 14-day-minimum stay within our managed isolation and quarantine system. We also have the crucial package of rapid testing, contact tracing, and the isolation of anyone who is likely infectious and their close contacts. We also have the now-familiar alert levels which place limits on whether workplaces and schools can be open and how many people can gather together. 

Those are all the things that the government is responsible for. But there are also the layers of Swiss cheese we can apply as individuals. Things like washing our hands, wearing a mask, using the Covid Tracer App to keep track of where we’ve been and who with, as well as staying home when sick, and getting tested if we have any symptoms that could be Covid-19. 

And now we have a new slice of cheese: vaccines. This week the first batches of the Pfizer/BioNTech vaccines safely arrived in the country. They passed all the quality control checks and now they are being rolled out to our border and managed isolation and quarantine workers and their families. Given they are most at risk from catching Covid-19, vaccinating them will help keep them safe. 

Keep up with your own slices of cheese

While there is lots of evidence that the vaccine is safe and effective at preventing Covid-19, it’s still not fully known whether the vaccine will stop people from transmitting the virus. That means it is very important that everyone in New Zealand remembers that we will still need to keep up with our layers of cheese till vaccines are available for everyone. So, keep using the Covid Tracer App, wearing a mask when required, and get tested if you lose your sense of smell, have any cold or flu-like symptoms, or develop a fever. 

In a few days, Toby and I will be back with an explainer on the Pfizer/BioNTech Covid-19 vaccine. If you’ve any questions, get in touch and we’ll try to answer them.

Keep going!