1. PRE-PANDEMIC VACCINATION MAY HALT THE SPREAD OF A PANDEMIC MATHEMATIC MODELING

2. CROSS PROTECTION Avian H5N1 influenza vaccination – now? PRE-PANDEMICPANDEMIC 3-4 weeks ? Months or years Direct protection Manufacturing of pre-pandemic vaccine Currently, at-risk population (poultry workers, vets, lab workers etc for vaccination now?) WHO Pandemic Alert

3. Longini et al. Science 2005; 309: 1083-1087 Prepandemic vaccines may halt the spread and significantly reduce the impact of a pandemic (mathematical modelling) Rural population of 500,000 in Thailand Assumptions: start intervention after 21 days TAP (targeted antiviral prophylaxis) low vaccine efficacy – A vaccine efficacy for susceptibility (VES) of approximately 30% (30% reduction in probability of being infected upon exposure) – A vaccine efficacy for infectiousness (VEI) of approximately 50% (50% reduction in probability of infecting someone else through contact) Practical example of modeling

4. Mathematical models have demonstrated that prepandemic vaccines may halt the spread and significantly reduce the impact Longini et al. Science 2005; 309: 1083-1087 *Targeted antiviral prophylaxis Simulated pandemic influenza outbreak (R0 = 1.7) without intervention compared to 80% TAP + 50% vacc. With Intervention (pre-pan vacc plus TAP) Without intervention

5. Vaccination as early as Day 30 could help reduce impact of pandemic Cumulative attack rate Vaccination from day 90 Vaccination from day 60 Vaccination from day 30 No Vaccination 34% 1% 13% 31% 0%10%20%30%40% Most people are likely to be exposed to pandemic flu before they can be vaccinated Policy of mass vaccination assuming 1% of the population can be vaccinated per day Ferguson et al. Nature 2006; 442(7101):448-52 US Model