title: Differential effects of pandemic (H1N1) 2009 on remote and indigenous groups, Northern Territory, Australia, 2009.
abstract: Pandemic (H1N1) 2009 influenza spread through the Northern Territory, Australia, during June-August 2009. We performed 2 cross-sectional serologic surveys on specimens from Northern Territory residents, with 445 specimens obtained prepandemic and 1,689 specimens postpandemic. Antibody titers were determined by hemagglutination inhibition against reference virus A/California/7/2009 on serum samples collected opportunistically from outpatients. All specimens had data for patients' gender, age, and address, with patients' indigenous status determined for 94.1%. Protective immunity (titer >40) was present in 7.6% (95% confidence interval [CI] 5.2%-10.1%) of prepandemic specimens and 19.5% (95% CI 17.6%-21.4%) of postpandemic specimens, giving a population-standardized attack rate of 14.9% (95% CI 11.0%-18.9%). Prepandemic proportion of immune persons was greater with increasing age but did not differ by other demographic characteristics. Postpandemic proportion of immune persons was greater in younger groups and around double in indigenous persons. Postpandemic proportion immune was geographically heterogeneous, particularly among remote-living and indigenous groups.
authors: Centre for Disease Control, Tiwi, Northern Territory, Australia. james.trauer@austin.org.au
authors: James McCracken
authors: JM
authors: Trauer
authors: Karen Louise
authors: KL
authors: Laurie
authors: Joseph
authors: J
authors: McDonnell
authors: Anne
authors: A
authors: Kelso
authors: Peter Gregory
authors: PG
authors: Markey
mesh_terms: D056704:Adaptive Immunity; D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood; D002648:Child; D003430:Cross-Sectional Studies; D006801:Humans; D015994:Incidence; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007251:Influenza, Human / Q000208:ethnology* / Q000276:immunology / Q000821:virology; D008875:Middle Aged; D015876:Northern Territory / Q000453:epidemiology; D058873:Pandemics; D012044:Regression Analysis; D012424:Rural Population; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral