Dynamics of SARS-CoV-2 and host immunity in infection and vaccine protection

Once challenged by the SARS-CoV-2 virus, the human host immune system triggers a dynamic process against infection. We constructed a simplistic mathematical model to describe host innate and adaptive immune response to viral challenge. Based on the dynamic properties of viral load and immune response, we classified the resulting dynamics into four modes, corresponding to the increasing severity of COVID-19 disease. We found immune efficacy against viral attack, clearance of infected cells, and IL-6 levels to be prognostic determinants, especially for severe and critical patients. We also investigated vaccine-induced protection against SARS-CoV-2 infection. Results strongly suggested that immune efficacy based on memory T cells, as well as neutralizing antibody titers, could be true indicators of vaccine protection rates. Finally, we analyzed infection dynamics of SARS-CoV-2 variants within the construct of our mathematical model. Overall, our results provide a systematic framework for understanding the dynamics of host response upon challenge by SARS-CoV-2 infection, and this framework can be used to predict vaccine protection and perform clinical diagnosis.