Figure 1.

Adding complexity to a simple Susceptible-Exposed-Infectious-Recovered (SEIR) model to realistically model public health interventions^a

Abbreviations: ICU, intensive care unit; NPIs, non-pharmaceutical interventions; VOC, variant of concern

^a The left hand diagram shows the structure of a simple Susceptible-Exposed-Infectious-Recovered (SEIR) model, next to which are examples of the factors that had to be introduced to realistically model COVID-19 transmission with emerging VOCs, and the use of NPIs and vaccinations, resulting in a complex model structure (right-hand diagram). In this case, the complex model is the Public Health Agency of Canada agent-based model, as described, in an earlier form, in Ng et al., 2020 ((30))