According to the Clinical Trials Registry India, 1,600 volunteers of more than or equal to 18 years will be enrolled in the study across 17 sites in the country. Of them, 400 participants will be part of the immunogenicity cohort. They will be randomly assigned on a 3:1 ratio to receive either Covishield or Oxford/AZ-ChAdOx1 nCoV-19. The rest of the 1,200 volunteers from the safety cohort, also randomly assigned in a 3:1 ratio, will receive either Covishield or placebo. Covishield was made from ChAdOx1 virus, a weakened version of a common cold virus that causes infections in chimpanzees that has been genetically changed. Genetic material has been added which is used to make proteins from the SARS-CoV-2 virus called spike glycoprotein. By vaccinating, researchers hope the body will recognise and develop an immune response to the spike protein that will help stop the coronavirus from entering human cells and prevent infection. x