BCG vaccination to decrease childhood infection and allergies

Two toddlers playing

Freya Harewood of the Murdoch Children's Infectious Diseases and Microbiology Group explains how one cheap and available vaccine could have significant impact on reducing the burden of illness, and potentially even allergies, in children. The vaccine in question is likely known to many Australian parents - the Bacillus Calmette-Guérin (BCG) vaccine – if it is unfamiliar to you, understanding the potential added benefits to this vaccine could be paramount to your child’s health. Freya shares the focus of her research:

Currently BCG is administered to over 120 million infants worldwide each year to prevent tuberculosis, an infection often without symptoms that typically affects the lungs. In comparison to unvaccinated children, those vaccinated with BCG have been found to have half the mortality in the first year of life. The positive effects of the vaccine are thought to be far greater than the reduced tuberculosis death rate, with the protection against other infections also noted.

BCG has also been associated with reduced allergies. These additional effects are termed ‘heterologous’ as they are not the intended outcomes of using the vaccine, but can nonetheless greatly impact health.

In Australia, routine administration of BCG was discontinued in the 1980s because of the low prevalence of tuberculosis. This means Australian children are not receiving the potential heterologous benefits of BCG. We are investigating the heterologous effects of BCG vaccination to understand and identify the immune-boosting component. We may then be able to include this component in vaccines that are routinely given in Australia. We can also ensure that this component is not lost in future redevelopments of the BCG vaccine to ensure our children continue to be protected.

This project is being undertaken in Melbourne through a large randomised controlled trial called MIS BAIR (Melbourne Infant Study: BCG for Allergy and Infection Reduction) in which 1400 infants are being recruited to receive, or not receive, BCG vaccine at birth. The effects of BCG vaccine are then investigated through serial blood tests and questionnaires over the first year of life.

The effects of BCG on the immune system are being investigated at a cellular level with particular focus on the training of their immune system. We aim to find key differences that correlate with the participants [or infant’s] clinical features. For example, we expect the number of particular inflammatory cells, or the way that these cells respond to other infections to differ depending on whether or not they received the BCG vaccine. We also expect differences in the number of clinical infections and the degree of allergies between the two groups.

Ultimately, through understanding the heterologous effects of BCG vaccine we could change the trajectory of health in children and contribute to decreased childhood infection and allergies.

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