Poster Presentation BacPath 13: Molecular Analysis of Bacterial Pathogens Conference 2015

Gonococcal vaccines: What is needed to reduce prevalence? (#134)

Andrew P. Craig 1 , Richard T. Gray 1 , Jennifer L. Edwards 2 , Michael A. Apicella 3 , Michael P. Jennings 4 , David P. Wilson 1 , Kate L. Seib 4
  1. The Kirby Institute, UNSW, Sydney, NSW, Australia
  2. Center for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital, Columbus, OH, United States
  3. Department of Microbiology, University of Iowa, Iowa City, IA, United States
  4. Institute for Glycomics, Griffith University, Gold Coast, QLD, Australia

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.