There is increasing evidence that allergic disorders result from an imbalance in the Th1 and Th2 immune responses. BCG vaccination has been shown to augment Th1 biased response and hence give protection against developing allergies. India has followed BCG vaccination under its Universal Immunization Programme (UIP) and is also a country with low prevalence of asthma according to ISAAC surveys. This community based study was conducted to explore a link between BCG vaccination and prevalence of asthma.
School children (n:10028, age group10-15 years) belonging to Chandigarh, India were examined to find the association between prevalence of BCG scar positivity and diagnosis of asthma, allergic rhinitis and eczema with the help of a questionnaire based survey followed by clinical investigations. The prevalence of other confounding factors such as indoor and outdoor environmental, dietary habits, family size and other childhood immunizations were also studied.
BCG scar was found in 7792 children . Allergic disorders were found in 536 (5.34%) children out of which 391 (5.01%) belonged to BCG scar positive group and 145 to the BCG scar negative group (6.48%). Prevalence of asthma, allergic rhinitis and eczema were all individually higher (p<.005) in the BCG scar negative group. BCG vaccination emerged as an independent factor influencing the prevalence of allergic disorders in children.
BCG scar positivity is associated with lower prevalence of allergic disorders in Indian children. Acknowledgement: Funding and support by ICMR Task Force for Asthma. Indian Council of Medical Research (ICMR), New Delhi.
BCG vaccination must be tried in a double blind randomized controlled trial in BCG scar negative children with respiratory allergy.
M. Singh, None.