title: Febrile seizures following measles and varicella vaccines in young children in Australia.
abstract: BACKGROUND
  Febrile seizures (FS) are common in childhood with incidence peaking in the second year of life when measles and varicella-containing vaccines are administered. This study aimed to examine the vaccine-attributable risk of FS following separate administration of MMR and monovalent varicella vaccines (VV) prior to a planned change to MMRV as the second dose of measles-containing vaccine at 18 months of age.
  
  
  METHODS
  All FS cases in children aged <5 years from 1st January 2012 to 30th April 2013 were identified from emergency department (ED) and inpatient databases at five Australian tertiary paediatric hospitals participating in PAEDS (Paediatric Active Enhanced Disease Surveillance). Immunization records were obtained from the Australian Childhood Immunization Register (ACIR). The relative incidence (RI) of FS following MMR dose 1 (MMR1) and VV in children aged 11-23 months was determined using the self-controlled case series (SCCS) method and used to calculate attributable risk.
  
  
  RESULTS
  There were 2013 FS episodes in 1761 children. The peak age at FS was 18 months. The risk of FS was significantly increased 5-12 days post receipt of MMR1 at 12 months (RI=1.9 [95% CI: 1.3-2.9]), but not after VV at 18 months (RI=0.6 [95% CI: 0.3-1.2]. The estimated excess annual number of FS post MMR1 was 24 per 100,000 vaccinated children aged 11-23 months (95% CI=7-49 cases per 100,000) or 1 per 4167 doses.
  
  
  CONCLUSIONS
  Our study detected the expected increased FS risk post MMR1 vaccine at 12 months, but monovalent varicella vaccine at age 18 months was not associated with increased risk of FS. This provides baseline data to assess the risk of FS post MMRV, introduced in Australia as the second dose of measles-containing vaccine at 18 months of age in July 2013.
authors.affiliation: National Centre for Immunization Research & Surveillance, Westmead, NSW, Australia; Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia; Children's Hospital Westmead, Sydney, Australia. Electronic address: kristine.macartney@health.nsw.gov.au.
authors.forename: Kristine K
authors.initials: KK
authors.lastname: Macartney
authors.affiliation: National Centre for Immunization Research & Surveillance, Westmead, NSW, Australia; School of Public Health and Community Medicine, UNSW Medicine, University of New South Wales, Sydney, NSW, Australia.
authors.forename: Heather F
authors.initials: HF
authors.lastname: Gidding
authors.affiliation: National Centre for Immunization Research & Surveillance, Westmead, NSW, Australia.
authors.forename: Lieu
authors.initials: L
authors.lastname: Trinh
authors.affiliation: National Centre for Immunization Research & Surveillance, Westmead, NSW, Australia.
authors.forename: Han
authors.initials: H
authors.lastname: Wang
authors.affiliation: National Centre for Immunization Research & Surveillance, Westmead, NSW, Australia.
authors.forename: Jocelynne
authors.initials: J
authors.lastname: McRae
authors.affiliation: Murdoch Children's Research Institute, Parkville, Australia; Royal Children's Hospital, Melbourne, Australia.
authors.forename: Nigel
authors.initials: N
authors.lastname: Crawford
authors.affiliation: Women and Children's Hospital, Adelaide, Australia; Robinson Research Institute and School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Gold
authors.affiliation: Royal Children's Hospital, Brisbane, Australia.
authors.forename: Anne
authors.initials: A
authors.lastname: Kynaston
authors.affiliation: Wesfarmer's Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, Perth, Australia; University of Western Australia School of Paediatrics and Child health, Princess Margaret Hospital, Perth, Australia.
authors.forename: Christopher
authors.initials: C
authors.lastname: Blyth
authors.affiliation: Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia; Children's Hospital Westmead, Sydney, Australia; Australian Paediatric Surveillance Unit, Westmead, Australia.
authors.forename: Zurynski
authors.initials: Z
authors.lastname: Yvonne
authors.affiliation: Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia; Children's Hospital Westmead, Sydney, Australia; Australian Paediatric Surveillance Unit, Westmead, Australia.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Elliott
authors.affiliation: National Centre for Immunization Research & Surveillance, Westmead, NSW, Australia; Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia; Children's Hospital Westmead, Sydney, Australia.
authors.forename: Robert
authors.initials: R
authors.lastname: Booy
authors.affiliation: Murdoch Children's Research Institute, Parkville, Australia; Paediatrics Department, The University of Melbourne, Melbourne, Australia.
authors.forename: Jim
authors.initials: J
authors.lastname: Buttery
authors.affiliation: Women and Children's Hospital, Adelaide, Australia; Robinson Research Institute and School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, Australia.
authors.forename: Helen
authors.initials: H
authors.lastname: Marshall
authors.affiliation: Royal Children's Hospital, Brisbane, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Nissen
authors.affiliation: Wesfarmer's Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, Perth, Australia; University of Western Australia School of Paediatrics and Child health, Princess Margaret Hospital, Perth, Australia.
authors.forename: Peter
authors.initials: P
authors.lastname: Richmond
authors.affiliation: National Centre for Immunization Research & Surveillance, Westmead, NSW, Australia; Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia; Children's Hospital Westmead, Sydney, Australia.
authors.forename: Peter B
authors.initials: PB
authors.lastname: McInytre
authors.affiliation: National Centre for Immunization Research & Surveillance, Westmead, NSW, Australia; Discipline of Paediatrics and Child Health, University of Sydney, Sydney, Australia; Children's Hospital Westmead, Sydney, Australia.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Wood
mesh_terms: D001315:Australia / Q000453:epidemiology; D019433:Chickenpox Vaccine / Q000009:adverse effects*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D022542:Measles-Mumps-Rubella Vaccine / Q000009:adverse effects*; D012307:Risk Factors; D003294:Seizures, Febrile / Q000453:epidemiology* / Q000209:etiology*; D017778:Vaccines, Combined
chemical_list: D019433:Chickenpox Vaccine; D022542:Measles-Mumps-Rubella Vaccine; D017778:Vaccines, Combined; C050102:measles, mumps, rubella, varicella vaccine
keywords: Febrile seizures; Measles–mumps–rubella vaccine; Risk; Vaccine safety; Varicella vaccine