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International Conference on Mathematical Biology and

Annual Meeting of The Society for Mathematical Biology,

July 27-30, 2009

University of British Columbia, Vancouver

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Program

Poster PS11B
Laura Matrajt
University of Washington and Fred Hutchinson Cancer Research Center
Title One Versus Two Doses: Best Vaccination Strategies for Pandemic Influenza
Abstract Vaccination remains one of the most effective interventions against pandemic influenza. Most of the current influenza A (H5N1) vaccines require two doses: a prime and a boost at least 3 weeks later. A possible novel influenza A (H1N1) vaccine is likely to require two doses as well. We developed a mathematical model to evaluate two strategies for optimally allocating limited vaccine supplies to determine if it is better to only prime a larger number of people or to vaccinate half as many with the full two doses. We aim to evaluate the effect of key parameters on the final illness attack rates (defined as the percentage of the population who became ill). We performed a thorough search in the parameter space for the following parameters: vaccination date, primary response level (defined as the percentage of the full vaccine efficacy that the vaccine will attain after the prime), vaccination coverage, concavity of the vaccine efficacies as functions of time, and the basic reproductive number R0. We compared final illness attack rates if full pre-pandemic vaccination (two doses) is used compared with reactive mass vaccination (after the beginning of the epidemic) with a single dose. There is a threshold in the values of R0: below which the strategy of fewer vaccinees/two doses gives lower final attack rates; above it, vaccinating more people with one dose is better. Though the threshold depends on all the parameters considered, the primary response levels are key. Our model differs from previous work in that it includes the primary response levels, and it models the vaccine efficacies dynamically. In the event of a vaccine shortage, our results could provide valuable insight for allocating limited resources. The model also highlights the need for better a understanding of the kinetics and better estimates of the vaccine efficacies.
CoauthorsIra M. Longini Jr.
LocationWoodward Lobby (Wednesday-Thursday)