title: Longitudinal seroepidemiologic study of the 2009 pandemic influenza A (H1N1) infection among health care workers in a children's hospital.
abstract: BACKGROUND
  To probe seroepidemiology of the 2009 pandemic influenza A (H1N1) among health care workers (HCWs) in a children's hospital.
  
  
  METHODS
  From August 2009 to March 2010, serum samples were drawn from 150 HCWs in a children's hospital in Taipei before the 2009 influenza A (H1N1) pandemic, before H1N1 vaccination, and after the pandemic. HCWs who had come into direct contact with 2009 influenza A (H1N1) patients or their clinical respiratory samples during their daily work were designated as a high-risk group. Antibody levels were determined by hemagglutination inhibition (HAI) assay. A four-fold or greater increase in HAI titers between any successive paired sera was defined as seroconversion, and factors associated with seroconversion were analyzed.
  
  
  RESULTS
  Among the 150 HCWs, 18 (12.0%) showed either virological or serological evidence of 2009 pandemic influenza A (H1N1) infection. Of the 90 unvaccinated HCWs, baseline and post-pandemic seroprotective rates were 5.6% and 20.0%. Seroconversion rates among unvaccinated HCWs were 14.4% (13/90), 22.5% (9/40), and 8.0% (4/50) for total, high-risk group, and low-risk group, respectively. Multivariate analysis revealed being in the high-risk group is an independent risk factor associated with seroconversion.
  
  
  CONCLUSIONS
  The infection rate of 2009 pandemic influenza A (H1N1) in HCWs was moderate and not higher than that for the general population. The majority of unvaccinated HCWs remained susceptible. Direct contact of influenza patients and their respiratory samples increased the risk of infection.
authors.affiliation: Department of Pediatrics, National Taiwan University Hospital, No, 8, Chung-Shan South Road, 10016 Taipei, Taiwan.
authors.forename: Ting-Yu
authors.initials: TY
authors.lastname: Yen
authors.forename: Chun-Yi
authors.initials: CY
authors.lastname: Lu
authors.forename: Luan-Yin
authors.initials: LY
authors.lastname: Chang
authors.forename: Yi-Ting
authors.initials: YT
authors.lastname: Tsai
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Huang
mesh_terms: D000328:Adult; D000914:Antibodies, Viral / Q000097:blood*; D015331:Cohort Studies; D005260:Female; D006282:Health Personnel; D006385:Hemagglutination Inhibition Tests; D006776:Hospitals, Pediatric; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D018570:Risk Assessment; D016036:Seroepidemiologic Studies; D013624:Taiwan / Q000453:epidemiology
chemical_list: D000914:Antibodies, Viral