Gardasil only protects against 4 genotypes... genotypes 6 and 11, the two most common low-risk (wart-causing) HPVs and genotypes 16 and 18, the two most common high-risk (dysplasia/cancer-causing) HPVs. there are over 150 genotypes, so if you're already infected with any high-risk genotype, Gardasil is a waste of money. that's why it's best used in teens who haven't become sexually active yet. even then, it's not full protection against warts or cancer.
And since HPV infection is a 'field' effect that starts the day you're born, you don't have to suck dick to get HPV in your mouth.... it gets in there through kissing, fingers and a host of other ways. same goes for your ass. sex DOES increase your exposure to more genotypes though.