  Contact matrices are an important ingredient in age-structured epidemic
models to inform the simulated spread of the disease between sub-groups of the
population. These matrices are generally derived using resource-intensive
diary-based surveys and few exist in the Global South or tailored to vulnerable
populations. In particular, no contact matrices exist for refugee settlements -
locations under-served by epidemic models in general. In this paper we present
a novel, mixed-method approach, for deriving contact matrices in populations
which combines a lightweight, rapidly deployable, survey with an agent-based
model of the population informed by census and behavioural data. We use this
method to derive the first set of contact matrices for the Cox's Bazar refugee
settlement in Bangladesh. The matrices from the refugee settlement show strong
banding effects due to different age cut-offs in attendance at certain venues,
such as distribution centres and religious sites, as well as the important
contribution of the demographic profile of the settlement which was encoded in
the model. These can have significant implications to the modelled disease
dynamics. To validate our approach, we also apply our method to the population
of the UK and compare our derived matrices against well-known contact matrices
previously collected using traditional approaches. Overall, our findings
demonstrate that our mixed-method approach can address some of the challenges
of both the traditional and previously proposed agent-based approaches to
deriving contact matrices, and has the potential to be rolled-out in other
resource-constrained environments. This work therefore contributes to a broader
aim of developing new methods and mechanisms of data collection for modelling
disease spread in refugee and IDP settlements and better serving these
vulnerable communities.
