Emerging Infectious Diseases (Aug 2011)

Risk Factors for Pandemic (H1N1) 2009 Seroconversion among Adults, Singapore, 2009

  • Wei-Yen Lim,
  • Cynthia H.J. Chen,
  • Yi Ma,
  • Mark I.C. Chen,
  • Vernon J.M. Lee,
  • Alex R. Cook,
  • Linda W.L. Tan,
  • Norberto Flores Tabo,
  • Ian Barr,
  • Lin Cui,
  • Raymond T.P. Lin,
  • Yee Sin Leo,
  • Kee Seng Chia

DOI
https://doi.org/10.3201/eid1708.101270
Journal volume & issue
Vol. 17, no. 8
pp. 1455 – 1462

Abstract

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A total of 828 community-dwelling adults were studied during the course of the pandemic (H1N1) 2009 outbreak in Singapore during June–September 2009. Baseline blood samples were obtained before the outbreak, and 2 additional samples were obtained during follow-up. Seroconversion was defined as a >4-fold increase in antibody titers to pandemic (H1N1) 2009, determined by using hemagglutination inhibition. Men were more likely than women to seroconvert (mean adjusted hazards ratio [HR] 2.23, mean 95% confidence interval [CI] 1.26–3.93); Malays were more likely than Chinese to seroconvert (HR 2.67, 95% CI 1.04–6.91). Travel outside Singapore during the study period was associated with seroconversion (HR 1.76, 95% CI 1.11–2.78) as was use of public transport (HR 1.81, 95% CI 1.05–3.09). High baseline antibody titers were associated with reduced seroconversion. This study suggests possible areas for intervention to reduce transmission during future influenza outbreaks.

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