This study tests the safety and effectiveness of a vaccine called **Bexsero** to prevent **gonorrhea**, a sexually transmitted infection. Bexsero is already approved to prevent a different disease, meningitis B, and this study will see if it can also help with gonorrhea. The trial involves adults 18-50 who are at higher risk for gonorrhea. Participants are randomly given either the vaccine or a placebo (a fake shot). Neither the participant nor the study staff know who gets what, making it "observer-blind." The study lasts about **16 months** for each participant, but takes around **36 months** to complete. Participants have several visits, including blood tests and swabs for testing. To join, you must be healthy, not pregnant, and willing to follow study rules. You cannot have received this vaccine before or have certain health conditions. The study aims to show if Bexsero can stop gonorrhea infections.

• The study lasts around 16 months for each participant.
• Participants need to attend several visits for tests and vaccinations.
• Participants must be healthy and free of certain infections to join.