A Gonococcal Vaccine Has the Potential to Rapidly Reduce the Incidence of Neisseria gonorrhoeae Infection Among Urban Men Who Have Sex With Men

Abstract

Background: A gonococcal vaccine is urgently needed due to increasing gonorrhea incidence and emerging multidrug-resistant gonococcal strains worldwide. Men who have sex with men (MSM) have among the highest incidences of gonorrhea and may be a key target population for vaccination when available.

Methods: An individual-based, anatomical site-specific mathematical model was used to simulate Neisseria gonorrhoeae transmission in a population of 10 000 MSM. The impact of vaccination on gonorrhea prevalence was assessed.

Results: With a gonococcal vaccine of 100% or 50% protective efficacy, gonorrhea prevalence could be reduced by 94% or 62%, respectively, within 2 years if 30% of MSM are vaccinated on presentation for sexually transmitted infection (STI) testing. Elimination of gonorrhea is possible within 8 years with vaccines of ≥ 50% efficacy lasting 2 years, providing a booster vaccination is available every 3 years on average. A vaccine's impact may be reduced if it is not effective at all anatomical sites.

Conclusions: Our study indicates that with a vaccine of modest efficacy and an immunization strategy that targets MSM presenting for STI screening, the prevalence of gonorrhea in this population could be rapidly and substantially reduced.

Keywords: Neisseria gonorrhoeae; gonococcal vaccine; gonorrhea; individual-based model; mathematical model; men who have sex with men (MSM); sexually transmitted infection.

Figure 1.

The impact on population gonorrhea prevalence of vaccines having a range of protective and transmission suppression efficacies, and 30% vaccine uptake. A and B, Gonorrhea prevalence during 10 years in the absence of a vaccine (baseline) or after the introduction of vaccination with vaccines having either (A) different levels of protective efficacy (0%–100%) with transmission suppression efficacy fixed at 50% or (B) different levels of transmission suppression efficacy (0%–100%) with protective efficacy fixed at 50%. In all scenarios, it is assumed that vaccine-conferred protection wanes after 2 years on average and that 30% per visit of unvaccinated individuals tested for sexually transmitted infections are vaccinated annually. The solid lines and shading are the median and interquartile range from 1000 model runs, respectively. C and D, Heatmaps showing the median (of 1000 model runs, with interquartile range listed in Supplementary Tables A3 and A4) gonorrhea prevalence at any anatomical site at year 2 (C) and at year 5 (D) after the introduction of vaccination with vaccines having different combinations of protective and transmission suppression efficacy.

Figure 2.

The impact on population gonorrhea prevalence of vaccines having a range of protective and transmission suppression efficacies, and 30% vaccine uptake. A and B, Gonorrhea prevalence during 10 years in the absence of a vaccine (baseline) or after the introduction of vaccination with vaccines having either (A) different levels of protective efficacy (0%–100%) with transmission suppression efficacy fixed at 50% or (B) different levels of transmission suppression efficacy (0%–100%) with protective efficacy fixed at 50%. In all scenarios, it is assumed that vaccine-conferred protection wanes after 2 years on average and that 30% per visit of unvaccinated individuals tested for sexually transmitted infections are vaccinated annually and that a vaccine booster is given every 3 years on average. The solid lines and shading are the median and interquartile range from 1000 selected model runs, respectively. C and D, Heatmaps showing the median (of 1000 model runs, with interquartile range listed in Supplementary Tables A5 and A6) gonorrhea prevalence at any anatomical site at year 2 (C) and at year 5 (D) after the introduction of vaccination with vaccines having different combinations of protective and transmission suppression efficacy.

Figure 3.

The impact on population gonorrhea prevalence with vaccines having a range of protective and suppressive efficacies, and 15% vaccine uptake. A and B, Gonorrhea prevalence during 10 years in the absence of a vaccine (baseline) or after the introduction of vaccination with vaccines having either (A) different levels of protective efficacy (0%–100%) with transmission suppression efficacy fixed at 50% or (B) different levels of transmission suppression efficacy (0%–100%) with protective efficacy fixed at 50%. In all scenarios, it is assumed that 15% per visit of unvaccinated individuals tested for sexually transmitted infections are vaccinated annually, and that vaccine-conferred protection wanes after 2 years on average. The solid lines and shading are the median and interquartile range from 1000 model runs, respectively. C and D, Heatmaps showing the median (of 1000 model runs, with interquartile range listed in Supplementary Tables A7 and A8) gonorrhea prevalence at any anatomical site at year 2 (C) and at year 5 (D) after the introduction of vaccination with vaccines having different combinations of protective and transmission suppression efficacy.

Figure 4.

The impact on population gonorrhea prevalence with vaccines having a range of protective and suppressive efficacies, and 60% vaccine uptake. A and B, Gonorrhea prevalence during 10 years in the absence of a vaccine (baseline) or after the introduction of vaccination with vaccines having either (A) different levels of protective efficacy (0%–100%) with transmission suppression efficacy fixed at 50% or (B) different levels of transmission suppression efficacy (0%–100%) with protective efficacy fixed at 50%. In all scenarios, it is assumed that 60% per visit of unvaccinated individuals tested for sexually transmitted infections are vaccinated annually, and that vaccine-conferred protection wanes after 2 years on average. The solid lines and shading are the median and interquartile range from 1000 model runs, respectively. C and D, Heatmaps showing the median (of 1000 model runs, with interquartile range listed in Supplementary Tables A9 and A10) gonorrhea prevalence at any anatomical site at year 2 (C) and at year 5 (D) after the introduction of vaccination with vaccines having different combinations of protective and transmission suppression efficacy.

Figure 5.

The impact on population gonorrhea prevalence of a vaccine that has reduced efficacy against oropharyngeal infection. A, Gonorrhea prevalence during 10 years in the absence of a vaccine (baseline) or after the introduction of vaccines with 50% protective efficacy and 50% transmission suppression efficacy at all anatomical site (red), or with 50% protective and transmission suppression efficacy at nonpharyngeal sites, but with both efficacies 25% (orange) or 0% at pharynx (yellow). In all scenarios, it is assumed that 30% per visit of unvaccinated individuals tested for sexually transmitted infections are vaccinated annually, and that vaccine-conferred protection wanes after 2 years on average. The solid lines and shading are the median and interquartile range from 1000 model runs, respectively. B and C, Heatmaps showing the median (of 1000 model runs, with interquartile range listed in Supplementary Tables A11 and A12) gonorrhea prevalence at any anatomical site at year 5 after the introduction of vaccines that have different combinations of protective and transmission suppression efficacy at nonpharyngeal sites (ie, efficacy at urethra and rectum only), with efficacies at the oropharynx reduced further by 50% (B) or 100% (C).

Figure 6.

The impact on population gonorrhea prevalence of a vaccine that suppresses symptoms. A, Gonorrhea prevalence during 10 years in the absence of a vaccine (baseline) or after the introduction of a vaccine with 50% protective efficacy and 50% transmission suppression efficacy that has no impact on symptoms (red) or that suppresses symptoms (orange), or a vaccine with 0% protective and transmission suppression efficacy but that suppresses symptoms (yellow). In all scenarios, it is assumed that 30% per visit of unvaccinated individuals tested for sexually transmitted infections are vaccinated, and that vaccine-conferred protection wanes after 2 years on average. The solid lines and shading are the median and interquartile range from 1000 model runs, respectively. B and C, Heatmaps showing the median (of 1000 model runs, with interquartile range listed in Supplementary Tables A13 and A14) gonorrhea prevalence at any anatomical site at year 2 (B) and at year 5 (C) after the introduction of vaccines that have different combinations of protective and transmission suppression efficacies, and that also suppress gonorrhea symptoms.