Universality and herd immunity threshold: Revisiting the SIR model for COVID-19

COVID-19 pandemic has been raging all around the world for almost a year now, as of November 1, 2020. In this paper, we try to analyze variation in different countries light some modifications susceptible-infected-recovered (SIR) model. The SIR model was modified by taking time-dependent rate parameters. From model, basic reproduction number, effective herd immunity, and immunity threshold are redefined. re-outbreak is real threat various countries. We have used above-mentioned quantities find reasons behind disease. Also, effectiveness prevent an epidemic analyzed with respect also tried show that there certain universal aspects spread containment disease short period time. Finally, current situation India attempted discuss possibilities order predict its future behaviour using our