Open Access Research article

Vaccination against 2009 pandemic H1N1 in a population dynamical model of Vancouver, Canada: timing is everything

Jessica M Conway12, Ashleigh R Tuite3, David N Fisman3, Nathaniel Hupert45, Rafael Meza1, Bahman Davoudi1, Krista English1, P van den Driessche6, Fred Brauer2, Junling Ma6, Lauren Ancel Meyers7, Marek Smieja8, Amy Greer39, Danuta M Skowronski10, David L Buckeridge1112, Jeffrey C Kwong133, Jianhong Wu14, Seyed M Moghadas14, Daniel Coombs2, Robert C Brunham1 and Babak Pourbohloul115*

Author Affiliations

1 Division of Mathematical Modeling, University of British Columbia Centre for Disease Control, 655 West 12th Avenue, V5Z 4R4 Vancouver, British Columbia, Canada

2 Department of Mathematics, University of British Columbia, Vancouver, British Columbia, Canada

3 Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada

4 Departments of Public Health and Medicine, Weill Medical College of Cornell University, New York, NY, USA

5 New York-Presbyterian Hospital, New York, NY, USA

6 Department of Mathematics and Statistics, University of Victoria, Victoria, British Columbia, Canada

7 Section of Integrative Biology, The University of Texas at Austin, Austin, TX, USA

8 Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada

9 Centre for Communicable Diseases and Infection Control, Public Health Agency of Canada, Toronto, Ontario, Canada

10 Epidemiology Services, British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada

11 Surveillance Lab, Department of Epidemiology and Biostatistics, McGill University, Montreal, Québec, Canada

12 Bureau de surveillance épidémiologique, Direction de santé publique de Montréal, Montréal, Québec, Canada

13 Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada

14 Centre for Disease Modelling, York University, Toronto, Ontario, Canada

15 School of Population and Public Health, Faculty of Medicine, University of British Columbia, Vancouver, Canada

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BMC Public Health 2011, 11:932  doi:10.1186/1471-2458-11-932

Published: 14 December 2011

Abstract

Background

Much remains unknown about the effect of timing and prioritization of vaccination against pandemic (pH1N1) 2009 virus on health outcomes. We adapted a city-level contact network model to study different campaigns on influenza morbidity and mortality.

Methods

We modeled different distribution strategies initiated between July and November 2009 using a compartmental epidemic model that includes age structure and transmission network dynamics. The model represents the Greater Vancouver Regional District, a major North American city and surrounding suburbs with a population of 2 million, and is parameterized using data from the British Columbia Ministry of Health, published studies, and expert opinion. Outcomes are expressed as the number of infections and deaths averted due to vaccination.

Results

The model output was consistent with provincial surveillance data. Assuming a basic reproduction number = 1.4, an 8-week vaccination campaign initiated 2 weeks before the epidemic onset reduced morbidity and mortality by 79-91% and 80-87%, respectively, compared to no vaccination. Prioritizing children and parents for vaccination may have reduced transmission compared to actual practice, but the mortality benefit of this strategy appears highly sensitive to campaign timing. Modeling the actual late October start date resulted in modest reductions in morbidity and mortality (13-25% and 16-20%, respectively) with little variation by prioritization scheme.

Conclusion

Delays in vaccine production due to technological or logistical barriers may reduce potential benefits of vaccination for pandemic influenza, and these temporal effects can outweigh any additional theoretical benefits from population targeting. Careful modeling may provide decision makers with estimates of these effects before the epidemic peak to guide production goals and inform policy. Integration of real-time surveillance data with mathematical models holds the promise of enabling public health planners to optimize the community benefits from proposed interventions before the pandemic peak.