title: Risk factors for pandemic (H1N1) 2009 seroconversion among adults, Singapore, 2009.
abstract: 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.
authors.affiliation: National University of Singapore-Epidemiology and Public Health, Yong Loo Lin School of Medicine, Singapore. wei-yen_lim@nuhs.edu.sg
authors.forename: Wei-Yen
authors.initials: WY
authors.lastname: Lim
authors.forename: Cynthia H J
authors.initials: CH
authors.lastname: Chen
authors.forename: Yi
authors.initials: Y
authors.lastname: Ma
authors.forename: Mark I C
authors.initials: MI
authors.lastname: Chen
authors.forename: Vernon J M
authors.initials: VJ
authors.lastname: Lee
authors.forename: Alex R
authors.initials: AR
authors.lastname: Cook
authors.forename: Linda W L
authors.initials: LW
authors.lastname: Tan
authors.forename: Norberto
authors.initials: N
authors.lastname: Flores Tabo
authors.forename: Ian
authors.initials: I
authors.lastname: Barr
authors.forename: Lin
authors.initials: L
authors.lastname: Cui
authors.forename: Raymond T P
authors.initials: RT
authors.lastname: Lin
authors.forename: Yee Sin
authors.initials: YS
authors.lastname: Leo
authors.forename: Kee Seng
authors.initials: KS
authors.lastname: Chia
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004196:Disease Outbreaks; D005260:Female; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D008297:Male; D058873:Pandemics; D012307:Risk Factors; D012846:Singapore / Q000453:epidemiology / Q000208:ethnology; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral