Gonorrhea, one of the most common sexually transmitted infections worldwide, can lead to serious sequelae, including infertility and increased HIV transmission. Recently, untreatable, multidrug-resistant Neisseria gonorrhoeae strains have been reported. In the absence of new antibiotics, and given the speed with which resistance has emerged to all previously used antibiotics, development of a vaccine would be the ideal solution to this public health emergency. Understanding the desired characteristics, target population, and expected impact of an anti-gonococcal vaccine is essential to facilitate vaccine design, assessment, and implementation. We have used mathematical modeling to fill these conceptual gaps and inform future gonococcal vaccine development.
Using an individual-based, epidemiological simulation model, gonococcal prevalence was simulated in a heterosexual population of 100, 000 individuals (with a ~1.7% prevalence rate) after the introduction of vaccines with varied efficacy (10-100%) and duration of protection (2.5-20 years). If a gonorrhea vaccine with 100% efficacy and 20 years duration of protection becomes available, our simulation modeling predicts over a 90% decrease in population prevalence within 15 years, provided all 13-year-olds are vaccinated. However, prevalence could also be reduced by at least 90% after 20 years, if all 13-year-olds were given a non-waning vaccine with 50% efficacy, or a vaccine with 100% efficacy that wanes after 7.5 years. While a 40% reduction in prevalence is achievable with a non-waning vaccine of only 20% efficacy. We also found that, if vaccines were restricted to just half of 13-year-olds, it would not matter whether they were females, males, or an even mix of the two sexes. We conclude that a vaccine of moderate efficacy and duration could have a substantive impact on gonococcal prevalence, and disease sequelae, if coverage is high and protection lasts over the highest risk period (i.e. most sexual partner change) among young people.