(A) Estimated R0 during the outbreak (mean and 95%CI), as a function of baseline R0 (i.e., that derived by using the contact matrix estimated for the baseline period). The figure refers to Wuhan and include both the scenario accounting for the estimated susceptibility to infection by age and assuming that all individuals are equally susceptible to infection. The distribution of the transmission rate is estimated through the next generation matrix approach by using 100 bootstrapped contact matrices for the baseline period in order to obtain the desired R0 values. We then use the estimate distribution of the transmission rate the bootstrapped outbreak contact matrices to estimate R0 for the outbreak period. The 95% confidence intervals account for the uncertainty on the distribution of the transmission rate, mixing patterns, and susceptibility to infection by age. (B) As (A), but for Shanghai. (C) Infection attack rate one year after the initial case of COVID-19 (mean and 95%CI) as a function of the baseline R0. The estimates are by simulating the SIR transmission model (see supplementary materials) using the contact matrix for the baseline period and considering the estimated susceptibility to infection by age and assuming that all individuals are equally susceptible to infection. The 95% confidence intervals account for the uncertainty on the mixing patterns and susceptibility to infection by age. (D) As (C), but for Shanghai.