Nothing. First off the vaccine is not composed of actual HPV DNA. Some vaccines are created by attenuating (reducing the strength) of the actual virus or organism. This is not the case with Gardasil. The vaccine utilizes what are called VLP's or virus like particles to create the immune response. If you have one particular strain of HPV, then the only thing that would happen is that the vaccine would not protect you against that particular strain but would protect you against the other three. Or if you had two strains, the other two and so on. Hope this helps.