We observed a 7-9 fold reduction in the daily number of social contacts during the intervention period in Wuhan and Shanghai (from 14.6 and 18.8 daily contacts respectively, to 2.0 and 2.3). During the period of social distancing interventions, 78-94% of contacts occurred with household members. Moreover, we estimated that children 0-14 years are less susceptible to SARS-CoV-2 infection than adults 15-64 years of age (odds ratio 0.34, 95%CI 0.24-0.49), while in contrast, individuals over 65 years are more susceptible to infection (odds ratio 1.47, 95%CI: 1.12-1.92). Armed with these data, we calibrate an age-specific COVID-19 transmission model and simulate the impact of social distancing and school closure. We show that a reduction in social contacts of the scale of that observed in Wuhan and Shanghai would have been sufficient to bring the COVID-19 epidemic under control. Finally, proactive school closure is estimated to reduce peak incidence by half and delay the epidemic, although these measures alone cannot interrupt transmission.

The results of our analysis are posted on a pre-print server: J. Zhang, M. Litvinova, Y. Liang, Y. Wang, W. Wang, S. Zhao, Q. Wu, S. Merler, C. Viboud, A. Vespignani, M. Ajelli, H. Yu. Changes in contact patterns shape the dynamics of the COVID-19 outbreak in China. Science eabb8001, 2020.