title: Vaccination history and risk of childhood leukaemia.
abstract: BACKGROUND
  Previous studies on vaccination and childhood leukaemia generated inconsistent results.
  
  
  METHODS
  In the Northern California Childhood Leukaemia Study, a case-control study with incident cases and matched birth certificate controls, detailed written vaccination records were collected. A total of 323 cases aged 0-14 years at diagnosis and 409 controls were included in this analysis. All vaccinations were censored on the reference date (date of diagnosis for cases and the corresponding date for matched controls). Conditional logistic regression analysis was conducted, adjusting for potential confounding factors. A primary variable of interest is the number of administrations (doses) of various types of vaccines.
  
  
  RESULTS
  Vaccinations against diphtheria, pertussis, tetanus, poliomyelitis, measles, mumps, and rubella were not associated with the risk of leukaemia. The odds ratio for each dose of Haemophilus influenzae type b (Hib) vaccine was 0.81 (95% CI 0.68-0.96). Compared with children who received two or fewer doses of Hib vaccine, those who received three or more doses had a significantly reduced risk of childhood leukaemia (odds ratio = 0.55, 95% confidence interval 0.32-0.94). The number of doses of hepatitis B vaccine received was not associated with leukaemia risk.
  
  
  CONCLUSIONS
  Hib vaccination is associated with a reduced risk of childhood leukaemia. Future studies with detailed exposure assessment and large sample sizes are needed to further address the role of vaccinations in the etiology of childhood leukaemia.
authors.affiliation: Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT 06520-8034, USA. xiaomei.ma@yale.edu
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Ma
authors.forename: Monique B
authors.initials: MB
authors.lastname: Does
authors.forename: Catherine
authors.initials: C
authors.lastname: Metayer
authors.forename: Carolyn
authors.initials: C
authors.lastname: Russo
authors.forename: Alan
authors.initials: A
authors.lastname: Wong
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Buffler
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004168:Diphtheria Toxoid / Q000009:adverse effects / Q000276:immunology; D004522:Educational Status; D005260:Female; D018073:Haemophilus Vaccines / Q000009:adverse effects / Q000276:immunology; D019741:Haemophilus influenzae type b / Q000276:immunology; D017325:Hepatitis B Vaccines / Q000009:adverse effects / Q000276:immunology; D006801:Humans; D007182:Income; D007223:Infant; D007938:Leukemia / Q000209:etiology* / Q000276:immunology; D008297:Male; D022542:Measles-Mumps-Rubella Vaccine / Q000009:adverse effects / Q000276:immunology; D010567:Pertussis Vaccine / Q000009:adverse effects / Q000276:immunology; D011051:Poliomyelitis / Q000276:immunology / Q000517:prevention & control; D012307:Risk Factors; D013745:Tetanus Toxoid / Q000009:adverse effects / Q000276:immunology; D014612:Vaccines / Q000009:adverse effects* / Q000276:immunology
chemical_list: D004168:Diphtheria Toxoid; D018073:Haemophilus Vaccines; D017325:Hepatitis B Vaccines; D022542:Measles-Mumps-Rubella Vaccine; D010567:Pertussis Vaccine; D013745:Tetanus Toxoid; D014612:Vaccines