History of vaccine: from centuries to present

The evolution of vaccines has proved to be a boon for humanity. From earlier times, vaccination has secured its importance and provides high protection against various diseases. Long since the immunization technique is in practice; however, variolation has been initiated from the Indian Peninsula and spread to China. Irrespective of the topographical birthplace of the vaccine, the variolation was one of the utmost research achievements in the 17th century by eradicated the smallpox disease. This inspiring vaccine development leads to the discovery of vaccines in an innovative form. Different types of vaccines like live attenuated/ killed, inactivated, whole pathogen, recombinant (DNA-based, mRNA-based, protein-based), the polysaccharide has successfully attributed in preventing many infectious diseases. These vaccines have been subdivided into different generations as per their evolution. Next-generation or third-generation vaccines are high in demand due to their extended-level protection and efficacy. In these precedent times of COVID-19, vaccines are the only source that can protect the entire nation. Over time, the development of vaccines gradually changing the world into a much securer place. This chapter discussed the origin of vaccination, its categorization in different generations, and present scenario of vaccines in the 21st century.