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MAGICS Lab

Nature Computational Science · 2022

Micro-level Social Structures and the Success of COVID-19 National Policies

Two numbers per country — household size and daily contacts — explain a lot of the pandemic's first wave.

Qingtao Cao, Babak Heydari

Pipeline schematic: household and contact micro-inputs feed a small-world contact network; a policy intervention removes weak ties; the resulting SEIR-style curve tracks cases over time.

Why did similar COVID-19 policies produce wildly different outcomes across countries? This paper builds an explainable, lightweight model where each country is a small-world contact network whose structure is set by just two numbers: average household size and average daily in-person contacts.

With no parameter calibration, the model reproduces the relative trajectory of confirmed cases across ten European countries through the first wave, and counterfactual analyses show how the right policy timing and stringency depend on these structural baselines — light and late can be enough in some countries while others need early and strict.