# Validating and Testing an Agent-Based Model for the Spread of COVID-19 in Ireland
## 4 Discussion
One example is that in the schools we model, we do not assign adult agents to be teachers. This could impact transmission between children and adults. In the real world, there is potential for transmission between students and staff in a school setting; however, some studies of COVID-19 transmission in schools in 2020 showed limited transmission in schools [35; 36]. Additionally, the model only simulates the spread of COVID-19 in the Republic of Ireland and not in Northern Ireland. Because we do not simulate the spread of COVID-19 across the entirety of Ireland, there might be some key transportation patterns between border counties that are not included in the simulation that played a part in driving the pandemic in those border areas. Another limitation is in our generated contact networks. There is no existing data set for Ireland that provides contact patterns between age groups. We use the Netherlands POLYMOD data [27] to determine the number of contacts agents have. While we think these data are an OK approximation for Irish contact patterns, we are introducing some uncertainty into the model with this assumption. Model uncertainty is also introduced in the choice of parameters determining the dynamics of COVID-19. The parameters we use come from the literature and, where possible, from literature on the spread of COVID-19 in Ireland. However, even in the literature, there is a wide range of values for the different parameters, for example, in a review from 2020, published values for \(R_{0}\) were found to range from 1.5 to 6.49 [37]. The selections we made for the model will impact the model output. The model was also created with the idea of looking at the short-term impacts of behavior changes or other interventions, so some assumptions, including assumptions around reinfections, were chosen with this in mind. This will likely impact the outcomes of the model if run for longer terms and for periods of the pandemic beyond 2020; thus, these assumptions would need to be adjusted. It is important to note that this model was created during the COVID-19 pandemic as a tool designed to simulate the spread of COVID-19 in Ireland to better understand what might happen in the short term. In this paper, the model is validated off 2020 data, and we test the model on an example where initial conditions surrounding the model are based off of cases in 2020. For much of 2020 and 2021, Ireland was in strict lockdown, where non-essential workers were asked to work from home, and at times individuals were not allowed to go beyond 5 km from their homes. The lockdown interventions that can be implemented in the model reflect the strict nature of Ireland's lockdowns. At the time of publication, the situation is vastly different from that of 2020. While there are still many cases and deaths worldwide, vaccinations and previous infections have reduced the likelihood of contracting COVID-19 and the severity of the disease when contracted. Additionally, the strict lockdowns and travel restrictions have been lifted in most countries. While the model was validated on 2020 data, we included the ability to turn on a number of other other characteristics of the model, for example, multiple variants with different levels of infectiousness, or vaccinations that can take into account waning immunity. The model has and is evolving as the pandemic evolves. However, we feel that while having a model that is validated off 2020 data is a limitation, it is also important to have such a model and understand what we can learn from it to better prepare ourselves for the next potential pandemic.