title: Utility of the first few100 approach during the 2009 influenza A(H1N1) pandemic in the Netherlands.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: National Institute for Public Health and the Environment (RIVM), PO box 1 3720 BA, Bilthoven, the Netherlands. Rianne.van.Gageldonk@rivm.nl.
authors.forename: Arianne B
authors.initials: AB
authors.lastname: van Gageldonk-Lafeber
authors.forename: Marianne Ab
authors.initials: MA
authors.lastname: van der Sande
authors.forename: Adam
authors.initials: A
authors.lastname: Meijer
authors.forename: Ingrid Hm
authors.initials: IH
authors.lastname: Friesema
authors.forename: Gé A
authors.initials: GA
authors.lastname: Donker
authors.forename: Johan
authors.initials: J
authors.lastname: Reimerink
authors.forename: Mirna
authors.initials: M
authors.lastname: Robert-Du Ry van Beest Holle
authors.forename: Jan M
authors.initials: JM
authors.lastname: Prins
authors.forename: Leslie
authors.initials: L
authors.lastname: Isken
authors.forename: François G
authors.initials: FG
authors.lastname: Schellevis
authors.forename: Mariken Im
authors.initials: MI
authors.lastname: van der Lubben