Introduction: The sexually transmitted infection gonorrhoea is a global public health concern due to its high prevalence, the severe sequelae that can result from infection, and the increasing difficulty in treating infections caused by multi-drug resistant strains of N. gonorrhoeae (Ng).[1] The WHO and CDC have prioritised Ng as an urgent public health threat for which the development of a vaccine is needed. [2] Ng is a human pathogen that infects the lower genital tract, pharynx, and rectum, with varying degrees of complication depending on the sex of the patient. Lack of natural immunity and appropriate animal model have made vaccine development for Ng challenging. [3] Despite causing distinct diseases, N. gonorrhoeae and Neisseria meningitidis are closely related human pathogens, with 80–100% DNA homology and conservation of the majority of genes.[4, 5] A retrospective case-control study showed that people vaccinated with the N. meningitidis serogroup B vaccine MeNZB has a reduced rate of Ng infection compared to unvaccinated controls.[6] We are now conducting a randomised control trial with a similar N. meningitidis vaccine, 4CMenB, to determine if it provides protection against Ng. Aim: This study aims to investigate serum samples from 4CMenB-vaccinated humans to characterise vaccine-induced antibodies that are cross reactive with Ng. Method: ELISA and Western Blot assays were used to test serum samples from 20 vaccinated and 20 unvaccinated humans, to characterise IgG1, 2, 3, 4, IgA and IgM antibodies that cross react with Ng whole cells and Ng proteins. Results: There is a significant increase in serum antibodies in 4CMenB-vaccinated humans against Ng compared to the unvaccinated group. Further study is underway to determine the functionality of these antibodies for bactericidal activity against Ng.