https://www.acog.org/womens-health/experts-and-stories/the-l...

> The vaccine is still helpful even if you have already tested positive for HPV or have been sexually active for a while. Most HPV transmission happens when people first become sexually active. But women who have already tested positive for HPV usually aren’t positive for all nine types that we vaccinate for. So in some cases, we’ll recommend those patients get the vaccine if they haven’t already. And if you’re older – midlife age, and new on the dating scene and sexually active – you should ask your doctor about the vaccine too.

>[Note: The HPV vaccine can also be an important part of treatment for the cell changes caused by HPV infection. After the abnormal cells have been removed or destroyed, the HPV vaccine may help prevent abnormal cells from coming back. Read Human Papillomavirus (HPV): Infection and Vaccination for more information.]

https://www.acog.org/womens-health/faqs/hpv-vaccination