Bacille Calmette-Guérin (BCG) Vaccine and Atopy
Condition: Asthma; Eczema; Food Hypersensitivity
MeSH terms: Asthma; Hypersensitivity; Food Hypersensitivity
Study type: Observational

Summary: 
      The prevalence of asthma and allergic diseases is increasing worldwide. Infections and
      vaccinations in childhood may have an impact on the subsequent development of asthma and
      allergy. In Guinea-Bissau, the investigators previously found that Bacille Calmette-Guérin
      (BCG) vaccine was associated with reduction in atopy. Since then the investigators have
      conducted a randomised trial of BCG vaccine given at birth to low birth-weight infants. The
      present study aims to follow up children enrolled in the BCG randomised trial to assess for
      asthma and allergy later in childhood. Based on previous observations, the investigators
      expect children allocated to receive BCG at birth will have a reduction in allergy profile
      when compared to children who did not receive BCG at birth.
    

Detailed description: 
      Background: Prevalence of asthma and allergy is increasing worldwide, and the cause is
      unclear. Previous work by the Bandim Health Project and others has identified that infections
      and routine childhood vaccinations have an impact on the development of atopic sensitisation
      and allergic symptoms later in life. A number of these studies have found association between
      BCG vaccination and reduction in atopy and allergy. Only one randomised trial has been
      conducted of BCG vaccine to protect against allergy with inconclusive results. The present
      project provides the opportunity to follow-up children born low birth-weight who were
      randomised to receive BCG vaccine at birth or to receive BCG later in infancy as part of
      regular care.

      Hypothesis:

        -  Children given BCG vaccine at birth will have reduced prevalence of positive skin-prick
           test and allergic symptoms when compared with children who did not receive BCG at birth

        -  Early BCG vaccination will be associated with reduced prevalence of positive skin prick
           test and allergic symptoms

        -  Early DTP vaccination will be associated with increased prevalence of positive
           skin-prick tests and allergic symptoms

      Objectives:

        -  to examine the effects of environmental factors, including BCG, DTP and measles
           vaccines, on atopy (determined by skin-prick tests) and symptoms of asthma, eczema and
           food allergy

        -  to examine the sex-differential effects of vaccination on atopy and allergic symptoms

        -  to determine the association between faecal microbial diversity, atopy and food allergy

      Methods: children previously enrolled in NCT00146302 will followed up at home (currently aged
      3-9 years) and tested for atopic sensitisation with skin-prick tests and presence of allergic
      symptoms determined by questionnaire.

      Sample size: 812 children from the Bandim Health Project study area were enrolled in the
      randomised trial. The investigators anticipate to be able to follow up approximately 487 of
      these children, which will have the power to detect a 30% difference in atopic sensitisation
      between groups.
    

Observational model: Cohort
Time perspective: Retrospective
Sampling method: Probability Sample
Study population: 
        Children previously enrolled in NCT00146302 living within Bandim Health Project study area,
        Bissau
      
Biospecimen description: 
      Faecal samples are collected for analyses of parasites and microbes
    
Keywords: Bacille Calmette-Guérin; DTP; Vaccination; Allergy; Atopy; Guinea-Bissau