Optimal control strategy to control pandemic Covid-19 using MSILIHR_V Model Shahriar Seddighi Chaharborj, Jalal Hassanzadeh Asl and Babak Mohammadi Math. Model. Nat. Phenom., 17 (2022) 23 Published online: 01 August 2022 DOI: 10.1051/mmnp/2022015