Background: Over six centuries ago, the most fatal pandemic ever recorded in human history, the Black Death (The Plague), emerged with an estimated death toll of 75-200 million. At present, COVID-19 has surfaced causing over 5 million infected and 340 thousand deaths worldwide, with the numbers still rising. Objective: This paper focuses on the significance of the effective reproduction number (Rt ) in the epidemiology of SARS-CoV-2, to understand the time-dependent transmission pattern of this virus after intervention measures such as city lockdowns and social distancing. Studies done by various parties on estimating the Rt for different countries are discussed and interpreted. Results: It is found that all the countries studied still show an Rt of greater than 1, indicating that the COVID-19 outbreak is still ongoing. However, some countries are gradually keeping COVID-19 under control with a decreasing Rt after implementing intervention measures. Conclusion: COVID-19 is still spreading rapidly across the entire globe, and the soonest production of vaccines is expected to be early 2021, but it is estimated that it will take up to five years to be developed.