  In the wake of the COVID-19 pandemic many countries implemented containment
measures to reduce disease transmission. Studies using digital data sources
show that the mobility of individuals was effectively reduced in multiple
countries. However, it remains unclear whether these reductions caused deeper
structural changes in mobility networks, and how such changes may affect
dynamic processes on the network. Here we use movement data of mobile phone
users to show that mobility in Germany has not only been reduced considerably:
Lockdown measures caused substantial and long-lasting structural changes in the
mobility network. We find that long-distance travel was reduced
disproportionately strongly. The trimming of long-range network connectivity
leads to a more local, clustered network and a moderation of the "small-world"
effect. We demonstrate that these structural changes have a considerable effect
on epidemic spreading processes by "flattening" the epidemic curve and delaying
the spread to geographically distant regions.
