1 / 10

New vaccines mean new strategies: A theoretical exploration of the impact of HPV/HSV vaccines.

New vaccines mean new strategies: A theoretical exploration of the impact of HPV/HSV vaccines. Geoff Garnett Department of Infectious Disease Epidemiology, Imperial College, London. Department of Infectious Disease Epidemiology, Imperial College.

celine
Télécharger la présentation

New vaccines mean new strategies: A theoretical exploration of the impact of HPV/HSV vaccines.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. New vaccines mean new strategies: A theoretical exploration of the impact of HPV/HSV vaccines. Geoff Garnett Department of Infectious Disease Epidemiology, Imperial College, London. Department of Infectious Disease Epidemiology, Imperial College

  2. Standard Thinking: The Critical Vaccination Threshold, pc 1 Eradication 0.8 Persistence 0.6 Critical proportion, pc Measles 0.4 Rubella Hib 0.2 0 0 2 4 6 8 10 12 14 16 18 20 Basic Reproductive Rate, R0 • Efficacy of STD vaccines likely less than childhood vaccines. • Delivery of vaccines against STDs controversial? • Platform for vaccine targeting and delivery. Department of Infectious Disease Epidemiology, Imperial College

  3. Impact of vaccination sub elimination - simple theory Meaning of efficacy vital. Efficacy v Degree – protected from a fraction of challenges Prevalence 0.8 0.7 0.6 Take – fraction protected from all challenges 0.5 0.4 0.3 0 0.2 0.4 0.1 Take 0 0.8 1 0.8 0.6 0.4 0.2 0 Degree Department of Infectious Disease Epidemiology, Imperial College

  4. The impact of behavioural reversals on endemic prevalence - 50% vaccine efficacy Increased risk increases the basic reproductive number 1 Degree 0.8 0.6 Equilibrium prevalence Take 0.4 0.2 0 0 100 200 300 400 500 Percentage increase in risk behaviour Department of Infectious Disease Epidemiology, Imperial College

  5. Cohort vaccination - endemic HIV prevalence ‘Take’ type efficacy reduces susceptibility: 0.3 0.2 Proportion of sexually active adults infected 30 years after introducing vaccine 0.1 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Proportion of each cohort effectively vaccinated Department of Infectious Disease Epidemiology, Imperial College

  6. 16 14 12 10 8 6 4 2 0 Reducing the effective and basic reproductive rate Reduced Transmission probability Effectively vaccinated Endemic Prevalence (%) 0 20 40 60 80 100 Percent Department of Infectious Disease Epidemiology, Imperial College

  7. Risks of release from competition of more pathogenic strains? • Requires cross immunity • Requires that cross immunity not generated by vaccine • Requires that frequency dependent selection is limiting incidence of infection • What is additional influence of vaccination interacting with screening? • What is the impact of competing hazards in success of an HPV vaccine? Department of Infectious Disease Epidemiology, Imperial College

  8. All HR HPV All HR HPV; screening HR HPV w/o 16, 18 HR HPV w/o 16, 18; screening .0004 .0003 Incidence ICC per 100,000 .0002 .0001 0 20 40 60 80 Age Department of Infectious Disease Epidemiology, Imperial College

  9. 100 50 % reduction in CIS 0 0 50 100 % reduction in hazard of HPV infection Department of Infectious Disease Epidemiology, Imperial College

  10. Conclusions • STD vaccines with ‘limited’ efficacy could provide powerful intervention tools. • Impact of an HSV vaccine depends upon impact of viral shedding. • Targeting unlikely to be useful for vaccines against viral STDs. • HPV vaccination strategy needs to include ongoing effective screening. • Little risk of competitive release of virulent HPV types

More Related