PHI. The vaccination risk group included healthcare providers [66] , and individuals younger than 5 years (excluding younger than 12 months old) and older than 65 years [60] . The risk group for antiviral included symptomatic individuals below 15 years and above 55 years [60, 86] . The efficacy levels for the vaccine (δ in (9)) and antiviral (τ in (2)) were assumed to be 40% [44, 87] and 70%, respectively. We did not consider the use of antiviral for a mass prophylactic reduction of infection susceptibility due to the limited antiviral availability [9] and the risk of emergence of antiviral resistant transmissible virus strains [26] . We assumed a 90% target population conformance for both vaccination and antiviral treatment [64] . The immunity development period for the vaccine was taken as 10 days [61] .