  The COVID-19 pandemic has resulted in more than 14.5 million infections and
6,04,917 deaths in 212 countries over the last few months. Different drug
intervention acting at multiple stages of pathogenesis of COVID-19 can
substantially reduce the infection induced,thereby decreasing the mortality.
Also population level control strategies can reduce the spread of the COVID-19
substantially. Motivated by these observations, in this work we propose and
study a multi scale model linking both within-host and between-host dynamics of
COVID-19. Initially the natural history dealing with the disease dynamics is
studied. Later, comparative effectiveness is performed to understand the
efficacy of both the within-host and population level interventions. Findings
of this study suggest that a combined strategy involving treatment with drugs
such as Arbidol, remdesivir, Lopinavir/Ritonavir that inhibits viral
replication and immunotherapies like monoclonal antibodies, along with
environmental hygiene and generalized social distancing proved to be the best
and optimal in reducing the basic reproduction number and environmental spread
of the virus at the population level.
