India’s first indigenously developed Receptor Binding Domain (RBD) protein sub-unit vaccine for COVID-19, CORBEVAX, developed by Biological E Limited, is a “recombinant protein sub-unit” vaccine developed from the Receptor Biding Domain (RBD) of the spike protein on the virus’s surface is adjuvanted with CpG 1018 and alum, which helps the body to build the immune response against the virus.