In recent years researchers have linked rising allergy rates to improved hygiene and asked whether the Bacillus Calmette-Guérin (BCG) vaccine can reverse the trend. Existing data is inconclusive, but an Australian team has seen enough to run a 1,400-person trial into the effect of the vaccine.
The trial is now recruiting 1,400 babies, half of whom will receive the BCG vaccine. By tracking the rates of eczema, food allergies, hay fever, asthma and other hypersensitivity disorders in both treatment arms, the researchers hope to show whether administration of the vaccine is linked to a fall in disease rates. The BCG vaccine was phased out of Australian immunization schedules in the mid-1980s, and its fall roughly correlates with a rise in the number of asthmatics. In 1989, 8.5% of Australians had asthma. By 1995, the proportion had risen to 11.3%.
Researchers have speculated that the vaccine gives the immune system an early workout. "The theory is that in our over-clean world babies aren't exposed to enough good bugs shortly after birth and this sets the immune system off in the wrong direction. We believe BCG is a simple, safe and well-tolerated vaccine that we could use to replace that absence of early microbial exposure or of our clean start to life," University of Melbourne infectious disease expert Professor Nigel Curtis told News.com.au.
Other researchers have tested the theory, but most have run epidemiological studies. In April 2010 researchers published a meta-analysis of 23 such studies in the International Journal of Epidemiology. This paper found evidence to support the BCG hypothesis, but just 9 months later another meta-analysis reached the opposite conclusion. The running of a 1,400-person randomized controlled trial should clarify the issue.
Solid evidence showing the BCG shot cuts incidence of allergies could open a new market for the vaccine. Sanofi ($SNY) and others manufacture BCG vaccines, but falling rates of tuberculosis have softened demand in some markets. The U.S. never recommended the use of the BCG vaccine, but with the number of asthmatics growing 25% from 2001 to 2009, physicians need something to stem the rise of allergies. The Centers for Disease Control and Prevention estimates asthma cost the U.S. $56 billion in 2007.