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U.S. Antiviral Strategic National Stockpile Countermeasures for 2009 (H1N1) Pandemic Influenza. Lauren Ancel Meyers The University of Texas at Austin. Ned Dimitrov University of Texas, Austin Sebastian Goll University of Texas, Austin Babak Pourbohloul British Columbia CDC
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U.S. Antiviral Strategic National Stockpile Countermeasures for 2009 (H1N1) Pandemic Influenza Lauren Ancel Meyers The University of Texas at Austin Ned Dimitrov University of Texas, Austin Sebastian Goll University of Texas, Austin BabakPourbohloul British Columbia CDC Nathaniel Hupert CDC
Distributing federal antiviral SNS • Problem: 11 million of the 50 million antiviral courses in the federally-held portion of the US strategic national stockpile (SNS) were distributed pro rata in early May. Those courses were replenished. In addition, states were originally given funds to purchase 31 million courses; and 24 million were purchased. How should the remaining federally-held portion of the SNS be deployed geographically and temporally? • Modeling approach: Using a city-level US model of H1N1 transmission and a powerful optimization method, the Meyers’ group determined the optimal release schedule for the remaining courses.
Distributing federal antiviral SNS • Assumptions • Objective is to minimize number of cases of H1N1 over 12 month time horizon • H1N1 spreads between cities via ground and air travel and within cities according to a mass action SEIR model • R0=1.6; average latent period of 3 days; average infectious period of 6 days • Initial condition of 100,000 cases distributed proportional to city size • Locally held courses disappear with a halflife of two months through misuse, loss and other forms of wastage • Antivirals reduce transmission by a total of about 50% when used to treat H1N1 cases within 48 hours of symptom onset Their manuscript also presents results under other scenarios.
Distributing federal antiviral SNS • Results • At estimated current levels of uptake (~20% within 48 hours) antivirals cannot significantly reduce transmission. However, public health efforts to increase AV treatment rates cansignificantly curb transmission over the next 6-12 months. • The optimal distribution schedule for the remaining 50 million courses in the federally-held portion of the antiviral SNS is 5 million per month pro rata to states starting now. This is optimal across all levels of uptake. Slight departures from this, e.g., monthly distributions of 1M or 10M courses, are expected to perform significantly worse. • Prevalence-based distributions (courses are given proportional to local H1N1 prevalence) do not improve outcome. Thus there is no reason to consider this politically difficult option.