Study Purpose: This study tests a vaccine called Bexsero to see if it can prevent gonorrhea infections. Gonorrhea is a common infection that can affect body parts like the throat, anus, or genitals. The study focuses on adults ages 18 to 50 who are more likely to get this infection.

How it Works: Participants will be randomly chosen to receive either the Bexsero vaccine or a placebo (a harmless substance). This is a "blind" study, meaning neither the participants nor the study team will know who got the vaccine or placebo. The study lasts about 16 months for each person, with regular check-ins over the course of the study.

• **Time Commitment:** Participation lasts about 16 months, with regular visits.
• **Compensation:** Participants may receive compensation for their time and travel.
• **Risks:** Possible side effects may include soreness at the injection site or mild fever.

Eligibility: To join, participants must be in good health, between 18-50 years old, and willing to follow study rules. Some people, like those who have received a similar vaccine before or have certain health conditions, may not be eligible.