title: [A survey on serological epidemiology of influenza A (H1N1) 2009 in Beijing].
abstract: OBJECTIVE
  To investigate the immunological level against influenza A (H1N1) 2009 in Beijing and provide evidence to evaluate the developing trend of the disease.
  
  
  METHODS
  Between Nov. 27, 2009 and Dec. 23, 2009, subjects were randomly selected from patients in hospitals (infectious and respiratory diseases related departments were excluded), volunteers in blood donation center and healthy subjects attending the physical examination center. Questionnaire survey was conducted and serum samples were collected to detect the hemagglutination-inhibition (HI) antibody against influenza A (H1N1) 2009 virus.
  
  
  RESULTS
  856 subjects participated in this survey, and 127 showed positive HI antibody to this pandemic virus. The proportions of sero-positivity among 0 - 5, 6 - 17, 18 - 55, ≥ 56 year olds were 14.5%, 19.4%, 17.4% and 8.0% respectively (P = 0.009). There was no significant difference in the sero-positivity between males and females (P = 0.693). The age-adjusted positive rate was 15.8% in the population of Beijing. By multivariate logistic regression analysis, factors as age, acute respiratory symptoms and the rate of pandemic (H1N1) 2009 vaccination were significantly associated with sero-positivity of HI antibody to the influenza A (H1N1) 2009 virus.
  
  
  CONCLUSIONS
  Above 15% of the population in Beijing showed protective antibody against influenza A (H1N1) 2009 virus, indicating the development of immunological barrier to this disease had been formed, to some extent.
authors.affiliation: Institute of Infectious and Endemic Diseases Control, Beijing Center for Disease Contorl and Prevention, Beijing 100013, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Yang
authors.forename: Fang
authors.initials: F
authors.lastname: Huang
authors.forename: Wei-xian
authors.initials: WX
authors.lastname: Shi
authors.forename: Gui-lan
authors.initials: GL
authors.lastname: Lu
authors.forename: Li-Li
authors.initials: LL
authors.lastname: Tian
authors.forename: Shu-juan
authors.initials: SJ
authors.lastname: Cui
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Shuang
authors.initials: S
authors.lastname: Li
authors.forename: Bai-wei
authors.initials: BW
authors.lastname: Liu
authors.forename: Ying
authors.initials: Y
authors.lastname: Deng
authors.forename: Xing-huo
authors.initials: XH
authors.lastname: Pang
authors.forename: Quan-yi
authors.initials: QY
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000097:blood / Q000453:epidemiology* / Q000821:virology; D008297:Male; D008875:Middle Aged; D016036:Seroepidemiologic Studies; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral