Recombinant vaccines are made by genetic engineering, the process and method of manipulating the genetic material of an organism. In this case, the genes that code for a specific protein from each of the four virus types of HPV are expressed in yeast to create large quantities of the protein. The protein that is produced is purified and then used to make the vaccine. Because the vaccine only contains a protein, and not the entire virus, the vaccine cannot cause the HPV infection. It is the body's immune response to the recombinant protein(s) that then protects against infection by the naturally occurring virus. | 
