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Article: Searching for sharp drops in the incidence of pandemic A/H1N1 influenza by single year of age

TitleSearching for sharp drops in the incidence of pandemic A/H1N1 influenza by single year of age
Authors
Keywords2009 H1N1 influenza
Distribution
Aged
Curve fitting
Gender
Issue Date2012
PublisherPublic Library of Science. The Journal's web site is located at http://www.plosone.org/home.action
Citation
PLoS One, 2012, v. 7 n. 8, article no. e42328 How to Cite?
AbstractBACKGROUND: During the 2009 H1N1 pandemic (pH1N1), morbidity and mortality sparing was observed among the elderly population; it was hypothesized that this age group benefited from immunity to pH1N1 due to cross-reactive antibodies generated from prior infection with antigenically similar influenza viruses. Evidence from serologic studies and genetic similarities between pH1N1 and historical influenza viruses suggest that the incidence of pH1N1 cases should drop markedly in age cohorts born prior to the disappearance of H1N1 in 1957, namely those at least 52-53 years old in 2009, but the precise range of ages affected has not been delineated. METHODS AND FINDINGS: To test for any age-associated discontinuities in pH1N1 incidence, we aggregated laboratory-confirmed pH1N1 case data from 8 jurisdictions in 7 countries, stratified by single year of age, sex (when available), and hospitalization status. Using single year of age population denominators, we generated smoothed curves of the weighted risk ratio of pH1N1 incidence, and looked for sharp drops at varying age bandwidths, defined as a significantly negative second derivative. Analyses stratified by hospitalization status and sex were used to test alternative explanations for observed discontinuities. We found that the risk of laboratory-confirmed infection with pH1N1 declines with age, but that there was a statistically significant leveling off or increase in risk from about 45 to 50 years of age, after which a sharp drop in risk occurs until the late fifties. This trend was more pronounced in hospitalized cases and in women and was independent of the choice in smoothing parameters. The age range at which the decline in risk accelerates corresponds to the cohort born between 1951-1959 (hospitalized) and 1953-1960 (not hospitalized). CONCLUSIONS: The reduced incidence of pH1N1 disease in older individuals shows a detailed age-specific pattern consistent with protection conferred by exposure to influenza A/H1N1 viruses circulating before 1957.
Persistent Identifierhttp://hdl.handle.net/10722/169288
ISSN
2015 Impact Factor: 3.057
2015 SCImago Journal Rankings: 1.395
PubMed Central ID
ISI Accession Number ID

 

DC FieldValueLanguage
dc.contributor.authorJacobs, JHen_US
dc.contributor.authorArcher, BNen_US
dc.contributor.authorBaker, MGen_US
dc.contributor.authorCowling, BJen_US
dc.contributor.authorHeffernan, RTen_US
dc.contributor.authorMercer, Gen_US
dc.contributor.authorUez, Oen_US
dc.contributor.authorHanshaoworakul, Wen_US
dc.contributor.authorViboud, Cen_US
dc.contributor.authorSchwartz, Jen_US
dc.contributor.authorTchetgen, ETen_US
dc.contributor.authorLipsitch, Men_US
dc.date.accessioned2012-10-18T08:49:04Z-
dc.date.available2012-10-18T08:49:04Z-
dc.date.issued2012en_US
dc.identifier.citationPLoS One, 2012, v. 7 n. 8, article no. e42328en_US
dc.identifier.issn1932-6203-
dc.identifier.urihttp://hdl.handle.net/10722/169288-
dc.description.abstractBACKGROUND: During the 2009 H1N1 pandemic (pH1N1), morbidity and mortality sparing was observed among the elderly population; it was hypothesized that this age group benefited from immunity to pH1N1 due to cross-reactive antibodies generated from prior infection with antigenically similar influenza viruses. Evidence from serologic studies and genetic similarities between pH1N1 and historical influenza viruses suggest that the incidence of pH1N1 cases should drop markedly in age cohorts born prior to the disappearance of H1N1 in 1957, namely those at least 52-53 years old in 2009, but the precise range of ages affected has not been delineated. METHODS AND FINDINGS: To test for any age-associated discontinuities in pH1N1 incidence, we aggregated laboratory-confirmed pH1N1 case data from 8 jurisdictions in 7 countries, stratified by single year of age, sex (when available), and hospitalization status. Using single year of age population denominators, we generated smoothed curves of the weighted risk ratio of pH1N1 incidence, and looked for sharp drops at varying age bandwidths, defined as a significantly negative second derivative. Analyses stratified by hospitalization status and sex were used to test alternative explanations for observed discontinuities. We found that the risk of laboratory-confirmed infection with pH1N1 declines with age, but that there was a statistically significant leveling off or increase in risk from about 45 to 50 years of age, after which a sharp drop in risk occurs until the late fifties. This trend was more pronounced in hospitalized cases and in women and was independent of the choice in smoothing parameters. The age range at which the decline in risk accelerates corresponds to the cohort born between 1951-1959 (hospitalized) and 1953-1960 (not hospitalized). CONCLUSIONS: The reduced incidence of pH1N1 disease in older individuals shows a detailed age-specific pattern consistent with protection conferred by exposure to influenza A/H1N1 viruses circulating before 1957.-
dc.languageengen_US
dc.publisherPublic Library of Science. The Journal's web site is located at http://www.plosone.org/home.action-
dc.relation.ispartofPLoS Oneen_US
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.subject2009 H1N1 influenza-
dc.subjectDistribution-
dc.subjectAged-
dc.subjectCurve fitting-
dc.subjectGender-
dc.titleSearching for sharp drops in the incidence of pandemic A/H1N1 influenza by single year of ageen_US
dc.typeArticleen_US
dc.identifier.emailJacobs, JH: jhartman44@gmail.comen_US
dc.identifier.emailCowling, BJ: bcowling@hku.hk-
dc.identifier.authorityCowling, BJ=rp01326en_US
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.1371/journal.pone.0042328-
dc.identifier.pmid22876316-
dc.identifier.pmcidPMC3410923-
dc.identifier.scopuseid_2-s2.0-84864453832-
dc.identifier.hkuros211575en_US
dc.identifier.volume7en_US
dc.identifier.issue8, article no. e42328en_US
dc.identifier.isiWOS:000307184700044-
dc.publisher.placeUnited States-

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