title: Intussusception after monovalent human rotavirus vaccine in Australia: severity and comparison of using healthcare database records versus case confirmation to assess risk.
abstract: BACKGROUND
  Surveillance for intussusception (IS) has been recommended in countries using rotavirus vaccine, but can be resource intensive. There is little data about the relative severity of rotavirus vaccine-associated IS compared with other IS cases. We collected detailed clinical data on all cases to evaluate the validity of ICD coding for IS in routinely collected data and case severity.
  
  
  METHODS
  Hospitalizations and emergency department presentations coded as IS in infants aged <12 months from July 1, 2007, to June 30, 2010, were classified using Brighton criteria by case note review. We used self-controlled case series analysis to estimate IS risk after vaccination for all and only Brighton level 1 cases.
  
  
  RESULTS
  Of 179 unique episodes coded as IS, 110 (61%) met Brighton level 1 criteria; self-controlled case series analysis found a relative incidence of IS in days 1-7 after the first dose of RV1 of 11.1 (95% confidence interval: 2.6-48.0). When all coded episodes of IS were included, relative incidence was 4.0 (95% confidence interval: 1.3-12.7). The proportion of Brighton 1 cases requiring surgery was 39% for those within 21 days of vaccine receipt and 34% for others (P = 0.67).
  
  
  CONCLUSIONS
  Using ICD-coded cases without individual confirmation yielded a lower point estimate of risk for IS post rotavirus vaccination; however, the risk remained statistically compatible with that for chart confirmed cases only. Analysis using healthcare databases to evaluate risk of IS if conducted without case confirmation may be insufficient to confirm a low-level risk. IS episodes after vaccination were not more severe.
authors.affiliation: From the *National Centre for Immunisation Research and Surveillance (NCIRS), Westmead; †Discipline of Paediatrics and Child Health, University of Sydney; ‡Department of Microbiology and Infectious Diseases, The Children's Hospital at Westmead; §Immunisation Unit, NSW Ministry of Health; and ¶ Immunisation Unit, Health Protection, New South Wales, Australia.
authors.forename: Helen E
authors.initials: HE
authors.lastname: Quinn
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Wood
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Cannings
authors.forename: Aditi
authors.initials: A
authors.lastname: Dey
authors.forename: Han
authors.initials: H
authors.lastname: Wang
authors.forename: Robert I
authors.initials: RI
authors.lastname: Menzies
authors.forename: Sarah
authors.initials: S
authors.lastname: Moberley
authors.forename: Su
authors.initials: S
authors.lastname: Reid
authors.forename: Peter B
authors.initials: PB
authors.lastname: McIntyre
authors.forename: Kristine K
authors.initials: KK
authors.lastname: Macartney
mesh_terms: D016208:Databases, Factual; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D038801:International Classification of Diseases; D007443:Intussusception / Q000175:diagnosis* / Q000453:epidemiology* / Q000601:surgery; D007902:Length of Stay; D008297:Male; D009517:New South Wales / Q000453:epidemiology; D012189:Retrospective Studies; D018570:Risk Assessment; D022243:Rotavirus Vaccines; D012720:Severity of Illness Index; D014611:Vaccination
chemical_list: D022243:Rotavirus Vaccines