Hypothesis
Two doses of the 4CMenB meningococcal vaccine would reduce gonorrhoea incidence in gay and bisexual men, as observational studies suggested.
What failed
In the open-label MenGO trial with 2 years of 3-monthly follow-up, vaccination did not significantly reduce gonorrhoea incidence (IRR 0.78, 95% CI 0.40–1.51, p = 0.457), although it raised serum bactericidal titres against N. gonorrhoeae at 6 months.
Broken assumption
The cross-protection against gonorrhoea seen in observational studies of 4CMenB shows up in a randomised trial.
Why
The vaccine was immunogenic, but titres did not rise in men infected at vaccination. The authors note the trial was small, sized for an assumed efficacy above 67%, and disrupted by COVID-19.
From the published paper: Thng et al. npj Vaccines, 2026. ↗CC BY