Bacille Calmette-Guérin (BCG) Vaccine and Atopy

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.