Background
Neisseria gonorrhoeae has a significant global impact on sexual and reproductive health. No vaccines are currently licensed for prevention. However, a meta-analysis of observational studies reported that a meningococcal B (4CMenB) vaccine is associated with an estimated 38% reduced risk of incident N. gonorrhoeae infection. A single open-label randomized trial reported no statistically significant protection.
Methods
We conducted a multicenter, randomized, double-blind, placebo-controlled trial in men who have sex with men (MSM) aged 18–50 years. Participants were either HIV-negative and taking HIV pre-exposure prophylaxis (PrEP), or living with HIV, and had a documented diagnosis of N. gonorrhoeae or infectious syphilis within the preceding 18 months. They were randomly assigned 1:1 to receive two doses 3 months apart of either 4CMenB or placebo. Sexually transmitted infection screening including N. gonorrhoeae nucleic acid amplification tests on specimens from urogenital, anorectal, and oropharyngeal sites were performed quarterly over a two-year period. The primary outcome was the incidence of a first episode of N. gonorrhoeae infection in the per-protocol population, occurring at least four weeks after administration of the second scheduled dose. Secondary outcome included symptomatic, asymptomatic, and site-specific infections.
Results
Between July 2021 and May 2023, 654 participants were randomized, with 587 included in the primary analysis. The incidence of first episode N. gonorrhoeae was 48.1 per 100 person-years (160 events among 296 participants) in the 4CMenB group and 47.8 per 100 person-years (155 events among 291 participants) in the placebo group (incidence rate ratio (IRR), 1.01; 95% confidence interval [CI], 0.80 to 1.25; P=0.97) (Fig. 1), for a vaccine efficacy of –0.5% (95% CI, -26.16% to 19.93%). The vaccine efficacy for symptomatic infection was 5.50% (95% CI, -56.02 to 42.82); asymptomatic infection, -6.36% (95% CI, -47.47 to 23.19); and urogenital, anorectal, and oropharyngeal infections, -20.00% (95% CI, -90.24 to 23.86), -1.18% (95% CI, -32.95 to 22.97), and 2.58% (95% CI, -27.67 to 25.65), respectively. The incidence of serious adverse events did not differ significantly between groups.
Conclusions
The 4CMenB vaccine did not reduce N. gonorrhoeae incidence among MSM at high risk of gonorrhea.
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