Effect of repeated intradermal injections of heat-inactivated Mycobacterium bovis bacillus Calmette-Guerin in adult asthma

Background There are a number of reports in the Chinese medical literature from the last 30 years regarding the efficacy of repeated doses of heat-inactivated bacillus Calmette-Guerin (BCG) in established asthma. There is also epidemiological and experimental evidence that exposure to mycobacteria has the potential to suppress the development of asthma/atopy. Methods Thirty-one Mantoux-negative adults with stable moderately severe asthma who were skin prick test positive to house dust mite were randomized to receive one injection (0.1 mL) a week for 4 weeks of heat-inactivated BCG or normal saline. Markers of asthma severity (including peak flow, forced expiratory volume in 1 s, major and minor exacerbations, symptom scores and beta-agonist use), blood eosinophil and IgE levels were monitored for 3 months. Results There were no statistically significant differences between the treatment group and placebo for any of the outcome variables. The recruitment to the trial was halted early and the number of injections reduced in a number of patients due to excessive local reactions to BCG. Conclusions In addition to the lack of efficacy of repeated heat-inactivated BCG injections, the occurrence of severe local reactions will limit the therapeutic application of this approach in asthma.