COVID-19 has caused an unprece­dent­ed pub­lic health cri­sis and eco­nom­ic shock to the glob­al econ­o­my. While many coun­tries were affect­ed, regions with an old­er pop­u­la­tion and weak­er pub­lic health inter­ven­tions tend­ed to suf­fer more mor­bid­i­ty and mor­tal­i­ty. We devel­oped an open-source/open data age-spe­cif­ic and mul­ti­ple-stage sus­cep­ti­ble-exposed-infect­ed-recov­ered-hos­pi­tal­ized-quar­an­tined-dead (SEIR-HQD) mod­el Uti­liz­ing the lat­est esti­mates of epi­demi­o­log­i­cal para­me­ters and demo­graph­ic data, we mod­el the poten­tial effects of var­i­ous inter­ven­tions in four rep­re­sen­ta­tive cities with dif­fer­ent pop­u­la­tion struc­tures — New York, Los Ange­les, Daegu and Nairo­bi. Our mod­el­ing quan­ti­fies the val­ue of ear­ly inter­ven­tions, which avoid­ed an addi­tion­al 5%, 16%, 37% and 43% of the infec­tions in Daegu, Nairo­bi, New York and Los Ange­les, respec­tive­ly, com­pared to what has been observed in the four cities. Crit­i­cal­ly, we find that school clo­sures, work­ing from home, and reduc­tion in oth­er mobil­i­ty were most ben­e­fi­cial for younger pop­u­la­tion (0–19 years old), mid­dle-age (20–59 years old) pop­u­la­tion and old­er pop­u­la­tion (60 years and old­er), respec­tive­ly across each city. Specif­i­cal­ly, school clo­sure avoid­ed 25%, 18%, 16% and 12% of the infec­tions for the pop­u­la­tion under 20 years old in Daegu, Los Ange­les, New York and Nairo­bi, respec­tive­ly. A 50% and 80% pop­u­la­tion work­ing from home pol­i­cy avoids 8% and 15% of the infec­tions. Reduc­tion in mobil­i­ty was more effec­tive than the work­ing from home strat­e­gy. Any sin­gle social dis­tanc­ing pol­i­cy if enact­ed alone can delay the spread of COVID-19 but was unable to total­ly sup­press the infec­tion. Coor­di­nat­ed pol­i­cy action can be high­ly effec­tive. Increas­ing the quar­an­tine rate to 10% of infec­tious cas­es was more effec­tive than strict social dis­tanc­ing alone in this study, although togeth­er they can sup­press 80% of the epi­dem­ic. A com­bi­na­tion of mod­er­ate social dis­tanc­ing and quar­an­tine strate­gies was able to avoid 99% of the infections.