title: Early BCG vaccination and reduction in atopy in Guinea-Bissau.
abstract: BACKGROUND
  It has been proposed that certain viral and bacterial infections in early childhood may prevent allergic sensitization, by inducing Th1-type immune responses. This has led to speculation that mycobacterial vaccines might, through their Th1-stimulating properties, also protect against atopy.
  
  
  OBJECTIVE
  To investigate whether the prevalence of atopy is lower in children who have been vaccinated with BCG in infancy than in children who have not been vaccinated.
  
  
  METHODS
  We measured skin test reactivity to three allergens (Dermatophagoides pteronyssinus, D. farinae and cockroach) in 400 children, aged 3-14 years, as part of a follow-up study to examine the immune sequelae of measles in an urban area of Bissau, the capital of Guinea-Bissau in west Africa. Information on childhood vaccinations, including BCG in infancy, was available from child records. Of these children, 271 had been vaccinated with BCG (according to records) and 53 had not been vaccinated (no record and no BCG scar). Atopy was defined in two ways, according to the presence of any allergen reaction > or = 2 mm and any reaction > or = 3 mm.
  
  
  RESULTS
  Of the children who had received BCG vaccine, 57 (21%) were atopic (any reaction > or = 2 mm), compared with 21 (40%) of the unvaccinated children [odds ratio, after controlling for potential confounding factors, 0.19 (95% CI 0.06-0.59)]. When atopy was defined using the 3-mm criterion, the reduction in atopy associated with BCG was greater the earlier the age at vaccination, and the largest reduction was seen in children vaccinated in the first week of life.
  
  
  CONCLUSIONS
  BCG vaccination given early in infancy may prevent the development of atopy in African children.
authors.affiliation: Projecto de Saúde de Bandim, Apartado 861, Bissau, Guinea-Bissau.
authors.forename: P
authors.initials: P
authors.lastname: Aaby
authors.forename: S O
authors.initials: SO
authors.lastname: Shaheen
authors.forename: C B
authors.initials: CB
authors.lastname: Heyes
authors.forename: A
authors.initials: A
authors.lastname: Goudiaby
authors.forename: A J
authors.initials: AJ
authors.lastname: Hall
authors.forename: A W
authors.initials: AW
authors.lastname: Shiell
authors.forename: H
authors.initials: H
authors.lastname: Jensen
authors.forename: A
authors.initials: A
authors.lastname: Marchant
mesh_terms: D000293:Adolescent; D001500:BCG Vaccine / Q000627:therapeutic use*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006169:Guinea-Bissau / Q000453:epidemiology; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D015995:Prevalence; D011897:Random Allocation; D018571:Sentinel Surveillance; D012882:Skin Tests; D011795:Surveys and Questionnaires
chemical_list: D001500:BCG Vaccine