Agent-based modeling for SARS-CoV-2 epidemic prediction and intervention
assessment. A methodological appraisal
Abstract
Our purpose is to assess epidemiological agent-based models– or ABMs -
of the SARS-CoV-2 pandemic methodologically. The rapid spread of the
outbreak requires fast-paced decision-making regarding mitigation
measures. However, the evidence for the efficacy of non-pharmaceutical
interventions such as imposed social distancing and school or workplace
closures is scarce: few observational studies use quasi-experimental
research designs, and conducting randomized controlled trials seems
infeasible. Additionally, evidence from the previous coronavirus
outbreaks of SARS and MERS lacks external validity, given the
significant differences in contagiousness of those pathogens relative to
SARS-CoV-2. To address the pressing policy questions that have emerged
as a result of COVID-19, epidemiologists have produced numerous models
that range from simple compartmental models to highly advanced
agent-based models. These models have been criticized for involving
simplifications and lacking empirical support for their assumptions. In
order to address these voices and methodologically appraise
epidemiological ABMs, we consider AceMod (the model of the COVID-19
epidemic in Australia) as an example of the modeling practice. Our case
study shows that, although epidemiological ABMs involve simplifications
of various sorts, the key characteristics of social interactions and the
spread of SARS-CoV-2 are represented sufficiently accurately. This is
the case because these modelers treat empirical results as inputs for
constructing modeling assumptions and rules that the agents follow; and
they use calibration to assert the adequacy to benchmark variables.
Given this, we claim that the best epidemiological ABMs are models of
actual mechanisms and deliver both mechanistic and difference-making
evidence. Furthermore, the efficacy claims are not only internally valid
but also adequately describe the effects of interventions in the targets
of the models. We also discuss the limitations of ABMs and put forward
policy recommendations.