So give it to them at 18, if they want it.
The HPV vaccine series is recommended at age 11-12.
Let's be realistic. How many people are still virgins at 18? (Less than half.) With about 15% of kids having their first encounter before age 16, from a public health perspective, the challenge really is to get them the vaccine while they can still get full benefit from it.
I truly do not understand the mentality that a young woman deserves to be punished with cancer because she did not wait until she was married. And that is exactly how I interpret refusing to vaccinate your teens.