Although human mobility is considered critical for the spread of the new coronavirus disease (COVID-19) both locally and globally, the extent to which such an association is impacted by social vulnerability remains unclear. Here, using multisource epidemiological and socioeconomic data of US counties, we develop a COVID-19 pandemic vulnerability index (CPVI) to quantify their levels of social vulnerability and examine how social vulnerability moderated the influence of mobility on disease transmissibility (represented by the effective reproduction number, Rt) during the US summer epidemic wave of 2020. We find that counties in the top CPVI quintile suffered almost double in regard to COVID-19 transmission (45.02% days with an Rt higher than 1) from mobility, particularly intracounty mobility, compared to counties in the lowest quintile (21.90%). In contrast, counties in the bottom CPVI quintile were only slightly affected by the level of mobility. As such, a 25% intracounty mobility change was associated with a 15.28% Rt change for counties in the top CPVI quintile, which is eight times the 1.81% Rt change for those in the lowest quintile. These findings suggest the need to account for the vulnerability of communities when making social distancing measures against mobility in the future.

This study proposes a framework combining economic improvement and the disruption within family interactions to disentangle the effect of parental migration on left-behind children’s development. We proposed a concept of parental capital, which refers to the cultivated interactions between the primary caregiver and the child. The disruption effect is theorized here as loss in parental capital, that the decrease in frequency and stability of interactions between children and the primary caregiver caused by parental migration. This research draws on the 2012 China Urbanization and Labor Migration Survey (CULMS), a nationally representative dataset including a substantial migrant population. Our results show that the loss in parental capital mediates almost all of the adverse effects of parental absence. In addition, parental capital doesn’t significantly mediate the effect of father migration on children’s cognitive development, but it has substantial explaining power in the disadvantage of children with dual-parent migration.