Assessing the impact of contact tracing with an agent-based model for simulating the spread of COVID-19: The Irish experience

Contact tracing is an important tool in managing infectious disease outbreaks and Ireland used a comprehensive contact tracing program to slow the spread of COVID-19. Although the benefits of contact tracing seem obvious, it is difficult to estimate the actual impact contact tracing has on an outbreak because it is hard to separate the effects of contact tracing from other behavioural changes or interventions. To understand the impact contact tracing had in Ireland, we used an agent-based model that is designed to simulate the spread of COVID-19 through Ireland. The model uses real contact tracing data from the first year of the COVID-19 pandemic. We found that without contact tracing, and everything else held constant, a larger number of cases, hospital admissions, ICU admissions and deaths would have occurred. The model suggests that without contact tracing deaths from COVID-19 in Ireland during the first year of the pandemic could have increased by 80% (this equates to approximately 5,768 agents in the model). This modelling study is an important step in highlighting the impact that contact tracing had on the course of the COVID-19 pandemic. Although we use a model for Ireland, this method is applicable to any country or region.