Single-region simulation models were calibrated using two common measures of pandemic severity [35, 45, 46] : the basic reproduction number (R 0 ) and the infection attack rate (IAR). R 0 is defined as the average number of secondary infections produced by a typical infected case in a totally susceptible population. IAR is defined as the ratio of the total number of infections over the pandemic period to the size of the initial susceptible population. To determine R 0 , all infected cases inside the simulation were classified by generation of infection, as in [33, 43] . The value of R 0 was calculated as the average reproduction number of a typical generation in the early stage of the pandemic, with no interventions implemented (the baseline scenario) [33] . Historically, R 0 values for PI ranged between 1.4 and 3.9 [37, 43] . To attain similar values, we calibrated the hourly contact rates of mixing groups [77] (original rates were adopted from [46] ). For the four regions, the average baseline value of R 0 was 2.54, which represented a high transmissibility scenario. The values of regional baseline IAR averaged 0.538.