This study aims to understand how the **HPV vaccine** (a shot that helps protect against cancers caused by the human papillomavirus) creates long-lasting protection by producing high levels of antibodies, which are proteins that help fight off infections. Participants will receive three shots of the 9-valent HPV vaccine over six months. **Antibody responses** will be checked in blood, saliva, lymph nodes (part of the body's immune system), and bone marrow, which is the tissue inside bones where blood cells are made. - **Participants**: Adults aged 18-45, healthy, willing to provide blood/saliva samples, and undergo lymph node and bone marrow sampling. - **Study Duration**: Participants must be available for up to 2 years for sample collections and monitoring. - **Risks**: Involves multiple visits and procedures like blood draws and needle aspirations, which may cause discomfort. By joining, you'll help researchers understand how vaccines work and improve future vaccines. Note: If you've already received an HPV vaccine or have certain health conditions, you cannot participate.