A novel SEIAHR compartment model for accessing the impact of vaccination, intervention policies, and quarantine on the COVID-19 pandemic: a case study of most affected countries Brazil, India, Italy, and USA

In this study, an attempt has been made to formulate a novel SEIAHR deterministic compartmental model for the COVID-19 pandemic by incorporating additionally vaccinated and quarantined compartments. We obtained the basic reproduction number using the next-generation matrix approach. Thereafter, the stability of equilibrium points has been investigated using the basic reproduction number. Furthermore, we have studied the pandemic behaviour in four countries: Brazil, India, Italy, and the USA. We have fitted the proposed model to daily new cases and cumulative cases of the aforementioned countries using the nonlinear least square technique in MATLAB. Moreover, we have also estimated the best-fitted model parameters based on the available data. In addition, a numerical simulation of the model has been added to examine the influence of intervention policies, vaccination rates, vaccine efficacy, and quarantine. It was found that all the control policies had a positive impact on reducing the COVID-19 incidence.