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Utility of the first few100 approach during the 2009 influenza A(H1N1) pandemic in the Netherlands

Arianne B van Gageldonk-Lafeber1*, Marianne AB van der Sande12, Adam Meijer1, Ingrid HM Friesema1, Gé A Donker3, Johan Reimerink1, Mirna Robert-Du Ry van Beest Holle1, Jan M Prins4, Leslie Isken1, François G Schellevis35, Mariken IM van der Lubben1 and On behalf of the Dutch ZonMw Influenza A(H1N1) 2009 consortium

Author Affiliations

1 National Institute for Public Health and the Environment (RIVM), PO box 1 3720 BA, Bilthoven, the Netherlands

2 Utrecht University Medical Center, Julius Centre, Utrecht, the Netherlands

3 Netherlands institute for health services research (NIVEL), Utrecht, the Netherlands

4 Department of Internal Medicine, Division of Infectious Diseases, Tropical Medicine and AIDS, Academic Medical Center, Amsterdam, the Netherlands

5 Department of General Practice/EMGO + Institute, VU University Medical Center, Amsterdam, the Netherlands

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Antimicrobial Resistance and Infection Control 2012, 1:30  doi:10.1186/2047-2994-1-30

Published: 21 September 2012



To guide policy and control measures, decent scientific data are needed for a comprehensive assessment of epidemiological, clinical and virological characteristics of the First Few hundred (FF100) cases. We discuss the feasibility of the FF100 approach during the 2009 pandemic and the added value compared with alternative data sources available.


The pandemic preparedness plan enabled us to perform a case–control study, assessing patient characteristics and risk factors for experiencing symptomatic influenza A(H1N1)2009 infection and providing insight into transmission. We assessed to what extent timely and novel data were generated compared to other available data sources.


In May-December 2009, a total of 68 cases and 48 controls were included in the study. Underlying non-respiratory diseases were significantly more common among cases compared to controls, while a protective effect was found for frequent hand washing. Seroconversion was found for 7/30 controls (23%), and persisting high titers for 4/30 controls (13%). The labour-intensive study design resulted in slow and restricted recruitment.


The findings of our case–control study gave new insights in transmission risks and possible interventions for improved control. Nevertheless, the FF100 approach lacked timeliness and power due to limited recruitment. For future pandemics we suggest pooling data from several countries, to enable collecting sufficient data in a relatively short period.