Annals of Epidemiology
Volume 19, Issue 6 , Pages 432-436 , June 2009

Pooling of Confounders Did Not Induce Residual Confounding in Influenza Vaccination Studies

  • Rolf H.H. Groenwold, MD

      Affiliations

    • Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, the Netherlands
    • Corresponding Author InformationAddress correspondence to: R.H.H. Groenwold, MD, University Medical Center Utrecht, Julius Center for Health Sciences and Primary Care, PO BOX 85500, 3508 GA, Utrecht, the Netherlands. Tel.: 31-88-756-8874; fax: 31-88-756-8099.
    • ,
  • Eelko Hak, MSC, PhD

      Affiliations

    • Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, the Netherlands
    • Department of Epidemiology, University Medical Center Groningen, the Netherlands
    • ,
  • Arno W. Hoes, MD, PhD

      Affiliations

    • Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, the Netherlands

Received 3 October 2008 ,Accepted 5 February 2009.

References 

  1. Jefferson T, Rivetti D, Rivetti A, Rudin M, Di Pietrantonj C, Demicheli C. Efficacy and effectiveness of influenza vaccines in elderly people: A systematic review. Lancet. 2005;366:1165–1174
  2. Hak E, Buskens E, van Essen GA, de Bakker DH, Grobbee DE, Tacken MA, et al. Clinical effectiveness of influenza vaccination in persons younger than 65 years with high-risk medical conditions: the PRISMA study. Arch Intern Med. 2005;165:274–280
  3. Nichol KL, Nordin JD, Nelson DB, Mullooly JP, Hak E. Effectiveness of influenza vaccine in the community-dwelling elderly. N Engl J Med. 2007;357:1373–1381
  4. Jackson LA, Nelson JC, Benson P, Neuzil KM, Reid RJ, Psaty BM, et al. Functional status is a confounder of the association of influenza vaccine and risk of all cause mortality in seniors. Int J Epidemiol. 2006;35:345–352
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  7. Jansen AG, Sanders EAM, Hoes AW, van Loon AM, Hak E. Influenza- and respiratory syncytial virus-associated mortality and hospitalisations. Eur Respir J. 2007;30:1158–1166
  8. Hak E, van Loon S, Buskens E, van Essen GA, de Bakker D, Tacken MA, et al. Design of the Dutch prevention of influenza, surveillance and management (PRISMA) study. Vaccine. 2003;21:1719–1724
  9. Simonsen L, Taylor RJ, Viboud C, Miller MA, Jackson LA. Mortality benefits of influenza vaccination in elderly people: an ongoing controversy. Lancet Infect Dis. 2007;7:658–666
  10. Jackson LA, Jackson ML, Nelson JC, Neuzil KM, Weiss NS. Evidence of bias in estimates on influenza vaccine effectiveness in seniors. Int J Epidemiol. 2006;35:337–344
  11. Hak E, Hoes AW, Nordin J, Nichol KL. Benefits of influenza vaccine in US elderly—appreciating issues of confounding bias and precision. Int J Epidemiol. 2006;35:800–802
  12. Altman DG, Royston P. The cost of dichotomising continuous variables. Br Med J. 2006;332:1080
  13. Groenwold RH, Hoes AW, Nichol KL, Hak E. Quantifying the potential role of unmeasured confounders: the example of influenza vaccination. Int J Epidemiol. 2008;37:1422–1429
  14. Kleinbaum DG, Kupper LL, Muller KE, Nizam A. Applied Regression Analysis and Other Multivariable Methods. 3rd ed.. Pacific Grove, CA: Duxbury Press; 1998;
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  16. Miettinen OS. Stratification by a multivariate confounder score. Am J Epidemiol. 1976;104:609–620

 This study is part of a personal grant of Dr. E. Hak to study confounding in observational intervention studies by the Netherlands Scientific Organization (VENI no. 916.56.109). There are no conflicts of interest.

PII: S1047-2797(09)00059-3

doi: 10.1016/j.annepidem.2009.02.001

Annals of Epidemiology
Volume 19, Issue 6 , Pages 432-436 , June 2009

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