Scientists have recently discovered that an imbalance in immune proteins allows gonorrhoea to evade the body's defences in 3% of infections — a finding that could transform vaccine development for this global health threat, that is increasingly becoming resistant to antibiotics.
Gonorrhoea, caused by the bacterium Neisseria gonorrhoeae, is the second most common bacterial sexually transmitted infection worldwide, with over 82 million cases in 2020. Whilst symptoms in men with urethral infections were significantly more common, research found that women who had the infection also lead to serious health complications, such as ectopic pregnancy and infertility.
Dr Samantha McKeand, Dr Amanda Rossiter-Pearson and researchers from the University of Birmingham, in collaboration with colleagues at the University of Oxford, have uncovered a surprising immune system paradox: in some people, antibodies designed to fight gonorrhoea actually protect the bacteria from being destroyed.
The research, published 30th January 2026 in mBio, examined bacterial samples and blood from 283 people with gonorrhoea infections as part of the G-ToG clinical trial. They found that approximately 3% of patients produced "blocking antibodies" that prevented their immune system from killing the bacteria. The key was not simply having too many antibodies, but rather an imbalance between two specific types: IgG2 and IgG3, which stick to the surface of the bacteria.
While IgG3 normally helps the immune system kill N. gonorrhoeae, high levels of IgG2 can interfere with this process. When IgG2 binds in greater amounts, it prevents IgG3 from triggering the bacterial killing mechanism, effectively allowing the bacteria to evade the body’s defences.
Although there is still no licensed gonorrhoea vaccine following a century of research, a meningitis vaccine tested in New Zealand unintentionally reduced gonorrhoea rates by approximately 30%, proving that vaccine protection is possible. But to create a targeted gonorrhoea vaccine, researchers need to ensure it stimulates the right type of immune response.
