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, p c Eradication 0 0.2 0.4 0.6 0.8 1 02468101214161820 Basic Reproductive Rate, R 0 Persistence Measles Rubella Critical proportion, p c Hib Department of Infectious Disease Epidemiology, Imperial College Efficacy of STD vaccines likely less than childhood vaccines. Delivery of vaccines against STDs controversial? Platform for vaccine targeting and delivery.

3. 0 0.4 0.8 0 0.2 0.4 0.6 0.8 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Prevalence Take Degree Impact of vaccination sub elimination - simple theory Meaning of efficacy vital. Degree – protected from a fraction of challenges Take – fraction protected from all challenges Efficacy v 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 0 0.2 0.4 0.6 0.8 1 0100200300400500 Percentage increase in risk behaviour Equilibrium prevalence Degree Take Department of Infectious Disease Epidemiology, Imperial College

5. Proportion of each cohort effectively vaccinated Cohort vaccination - endemic HIV prevalence ‘Take’ type efficacy reduces susceptibility: 0 0.1 0.2 0.3 00.10.20.30.40.50.60.70.8 Proportion of sexually active adults infected 30 years after introducing vaccine Department of Infectious Disease Epidemiology, Imperial College

6. Reducing the effective and basic reproductive rate 0 2 4 6 8 10 12 14 16 020406080100 Percent Reduced Transmission probability Effectively vaccinated Endemic Prevalence (%) Department of Infectious Disease Epidemiology, Imperial College

7. Risks of release from competition of more pathogenic strains? 1)Requires cross immunity 2)Requires that cross immunity not generated by vaccine 3)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. Incidence ICC per 100,000 Age All HR HPV All HR HPV; screening HR HPV w/o 16, 18 HR HPV w/o 16, 18; screening 20406080 0.0001.0002.0003.0004 Department of Infectious Disease Epidemiology, Imperial College

9. % reduction in CIS % reduction in hazard of HPV infection 050100 0 50 100 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