The Swiss Cheese Model for COVID-19 is an excellent mental tool to visualize COVID-19 prevention strategies at the system level, a bird’s eye view.

First, about the Swiss Cheese Model. As emphasized by James Reason, the model’s creator, it invites us to view human errors as a consequence, not as a cause. According to this line of thinking, the error is not a moral problem but a system problem. I have discussed it in the above post.

Swiss Cheese Model for COVID-19

We can apply the Swiss Cheese Model for COVID-19 to visualize and understand COVID-19 prevention strategies. Academics and healthcare practitioners applied the model for this purpose. I will discuss their versions here.

The above image depicts my version. It features the following characteristics.

1. COVID-19 defence layers arranged in levels

The prevention strategies are categorized into three levels: Micro, Meso, and Macro. I bring this group nomenclature from the sociological literature. The following list clarifies what those terms refer to.

• Micro-level: Individual-level
• Meso – level: Group or community level
• Macro-level: Political/policy level

2. The levels in a hierarchical order

The levels are arranged in a hierarchical order. The macro-level layers yield the highest impact. The meso and micro-level layers follow each other respectively. The slices’ increase in size from micro to macro represents it.

3. Each level includes at least two defence layers (slices).

Each level includes at least two layers or strategies (two cheese slices). This is not comprehensive and requires modifications. These layers carry holes of varying sizes and shapes. The holes shift their positions and hence they are dynamic.

• Micro-level defence layers: Stay at home, face mask, and physical distancing
• Meso-level defence layers: Community support and lockdowns
• Macro-level defence layers: Paid sick leave and border control

4. The lower level is dependent upon the adjacent higher level.

Any level cannot withstand by itself; each layer depends on the adjacent one. The image depicts it.

The above list of prevention strategies is not complete, and the model deliberately omitted vaccines and testing because it aims to highlight the relative importance of standard preventive measures. Those interested can include any other measure.

Previous models

Few Swiss Cheese models for COVID-19 exist. The most popular one is the version of Ian Mackay, a virologist from Brisbane, Australia. The New York Times has reported it after his version went viral on Twitter. The following is his version.

I found a Sinhala version of Ian Mackay’s version of the Swiss Cheese Model.

The New Zealand version

Siouxsie Wiles, Associate Professor at the University of Auckland with Toby Morris introduced the following model. It is a very comprehensive one as you can see it. You can read about it in this post about COVID-19 and the Swiss cheese system.