TY - JOUR AU - Trauer, James McCracken AU - Laurie, Karen Louise AU - McDonnell, Joseph AU - Kelso, Anne AU - Markey, Peter Gregory T1 - Differential Effects of Pandemic (H1N1) 2009 on Remote and Indigenous Groups, Northern Territory, Australia, 2009 T2 - Emerging Infectious Disease journal PY - 2011 VL - 17 IS - 9 SP - 1615 SN - 1080-6059 AB - 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. KW - viruses KW - influenza A virus KW - H1N1 KW - influenza KW - serology KW - health services KW - pandemic (H1N1) 2009 KW - indigenous populations KW - high-risk populations KW - Australia KW - Northern Territory KW - research DO - 10.3201/eid1709.101196 UR - https://wwwnc.cdc.gov/eid/article/17/9/10-1196_article ER - End of Reference