The field of science that deals with the evaluation techniques and methods involved in the evaluation of vaccines is known as vaccine epidemiology. The overall aim of the field of research is to provide an understanding of various methods and techniques involved an evaluation of vaccines and immunization. Vaccines are among the most effective public health interventions against infectious diseases. The use of vaccines results in a profound alteration of the environment in which parasites live. Indeed, the goal of vaccination is to protect individual hosts and consequently decrease parasite prevalence. The benefits of vaccination, one of the most cost-effective public health interventions, have not fully reached target beneficiaries in many low- and middle-income countries. Though the field of vaccine research and vaccinology has received a lot of attention since the discovery of the smallpox vaccine by Edward Jenner (1749-1823) in 1798, more than two centuries later, an estimated 20% of deaths among children aged less than 5 years occur due to diseases preventable by currently licensed vaccines. Since the discovery of smallpox vaccine, a number of vaccines have become available. “Vaccine research and vaccinology” had witnessed a sort of ‘renaissances in vaccine research and uses’ in the early 1970s and 1980s, and now in the 21st century, there are licensed vaccines against nearly 27 agents and ongoing research on candidate vaccines against nearly 130 agents. Vaccine efficacy is the percentage reduction of disease in a vaccinated group of people compared to an unvaccinated group, using the most favorable conditions. Vaccine efficacy was designed and calculated by Greenwood and Yule in 1915 for cholera and typhoid vaccines.