title: Post-pandemic seroprevalence of 2009 pandemic influenza A (H1N1) virus in Shandong Province, China.
abstract: The purpose of this study was to understand the geographic extent, risk factors, and attack rate of  the 2009 pandemic influenza A (H1N1) virus [A(H1N1)pdm09] infection in Shandong Province, China and to  identify the influencing factors. A randomized serological survey of A(H1N1)pdm09 infection was carried out in  August and September 2010. A total of 4,549 participants involved in the survey had their antibody levels  tested by hemagglutination-inhibition assay. The overall seropositive rate for A(H1N1)pdm09 antibodies was  25.85%. The seropositive rate was 25.89% for the unvaccinated group, with statistically significant  differences among individuals of different age groups, occupations, and cities. The highest seropositive rate  was observed in young children aged 0-5 years and elderly people aged ≥60 years. Multivariate logistic  regression revealed that subjects in rural areas had significantly higher odds ratio of A(H1N1)pdm09 seropositivity  than those in the capital city. Individuals belonging to all professions, except for teachers, had  significantly lower odds ratio of A(H1N1)pdm09 seropositivity compared with children in family care. Our data  indicated that almost 26% of the residents in Shandong Province had appropriate antibody titers against  A(H1N1)pdm09. This seroepidemiology study provides valuable data for understanding the epidemiology of the  2009 pandemic influenza and for planning future intervention strategies; moreover, it highlights the  significance of seroprevelance studies.
authors.affiliation: Shandong University Institute for Prevention Medicine, Shandong, China.
authors.forename: Ti
authors.initials: T
authors.lastname: Liu
authors.forename: Zhong
authors.initials: Z
authors.lastname: Li
authors.forename: Shaoxia
authors.initials: S
authors.lastname: Song
authors.forename: Shengyang
authors.initials: S
authors.lastname: Zhang
authors.forename: Yulu
authors.initials: Y
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Lin
authors.forename: Shuang
authors.initials: S
authors.lastname: Wang
authors.forename: Xianjun
authors.initials: X
authors.lastname: Wang
authors.forename: Aiqiang
authors.initials: A
authors.lastname: Xu
authors.forename: Zhenqiang
authors.initials: Z
authors.lastname: Bi
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology / Q000302:isolation & purification*; D007252:Influenza Vaccines / Q000008:administration & dosage; D007251:Influenza, Human / Q000453:epidemiology* / Q000276:immunology / Q000821:virology*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D058873:Pandemics / Q000706:statistics & numerical data; D016036:Seroepidemiologic Studies; D014611:Vaccination / Q000706:statistics & numerical data
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines