Bacille Calmette-Guérin (BCG) vaccine could play a role in counteracting the rising prevalence of atopic diseases, say Melbourne clinicians who have been investigating whether neonatal BCG vaccination reduces the incidence of eczema in infants.
Paediatric infectious disease physicians involved in the Melbourne Infant Study BCG for allergy and infection say a single dose of the vaccine soon after birth could reduce the incidence of eczema in infants with two atopic parents.
The study saw 1272 infants randomised to receive BCG-Denmark or no BCG at birth.
Now 12-month follow-up data reveals the century-old vaccine, designed to protect against TB, significantly reduced the risk of developing eczema in a subgroup of infants – those most at risk for developing the condition.
Families involved in the trial completed 3-monthly questionnaires over 12 months. Eczema was also assessed using the UK diagnostic criteria at a 12-month clinic visit.
Overall, the 12-month eczema incidence was 32.2% in the BCG-group compared with 36.6% in the control group.
Though not statically significant, 15.7% of babies in the BCG-group vs. 19.2% in the control group had eczema lesions at the 12-month visit; 35.7% vs. 39.0% reported using topical steroids; and 7.3% vs. 10.2% had severe eczema scores.
But in the 344 high-risk infants – those with two atopic parents – the 12-month eczema incidence was 35.3% in the BCG-group compared with 46.8% in the control group.
It translates to a 25% relative risk reduction – or 11.5% absolute risk reduction – in the incidence of eczema compared to high risk infants who had not had the vaccine.
Dr Laure Pittet, clinical research fellow at the Royal Children’s Hospital in Melbourne and an investigator on the trial told the limbic that previous work in Africa had led to the suggestion that BCG-induced immunomodulation of the developing immune system might reduce the prevalence of allergic disease and asthma.
“In a randomised control trial set in Africa, researchers realised that infants who had received BCG had 50% lower all cause mortality – so, not linked to TB – compared to those infants who had BCG.”
Coupled with the ‘hygiene hypothesis – that reduced early expose to micro-organisms might have contributed to the rise in atopic disease – Dr Pittet suggests that neonatal BCG vaccination provides an early, controlled microbial exposure that might go on to reduce the incidence of eczema.
“By giving BCG at early age it promotes T helper (Th)1 immunity, suppressing atopy-mediating Th2 immunity. We found BCG does seem to have a modest effect on the overall cohort but where the effect is greatest is among pre-disposed infants – that’s where we found the greatest reduction with a a 25% decrease in eczema prevalence.”
Describing the findings as ‘interesting’, Dr Pittet said more work is needed before its use for eczema prevention is recommended.
“There might be an advantage for those at really high risk but, for the moment based on this study, there’s not sufficient evidence to recommend it.’
The group plans to follow patients longer term up to five years.
The study is published in The European Journal of Allergy and Immunology