Global mobility flows and COVID-19 spread in Europe during the emergency phase: Insights from Meta-Facebook data.

Human mobility within and between localities is a key determinant influencing the spatio-temporal spread of epidemic diseases. To investigate the role of the global mobility flows in shaping the cross-border transmission of COVID-19 in 30 EU/EEA countries, we analyzed individual mobility from Facebook Travel Patterns and integrated it into a multivariate endemic-epidemic model with fixed and random effects. The models were applied to country-specific surveillance data of weekly reported COVID-19 cases from 23 March 2020 to 18 December 2022. Additional datasets were also considered, such as the Stringency Index, vaccination coverage with assumed waning immunity of primary course and three booster doses, circulating SARS-CoV-2 variants of concern, and country population data. The study found that global mobility derived from empirical data has a valuable role in defining the spatio-temporal spread of COVID-19 during the emergency phase of the pandemic, that is, the diffusion of SARS-CoV-2 between European countries was likely driven by high-flux commuting between neighboring countries. The present approach offered a detailed understanding of disease transmission and enabled the study of fine-grained nuances in a unified framework that is both more pragmatic and less reliant on rigid assumptions.