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Clinical Trial
. 2025 Jun;36(6):e70110.
doi: 10.1111/pai.70110.

Neonatal BCG vaccination to prevent asthma: Results from the MIS BAIR randomized controlled trial

Laure F Pittet  1   2   3 , Emily K Forbes  1 , Susan Donath  2   4 , Kate L Francis  2   4 , Kaya Gardiner  1   5 , Katie L Flanagan  6   7   8 , Anne-Louise Ponsonby  9   10 , Roy Robins-Browne  1   11 , Frank Shann  2 , Mike South  2   12 , Peter Vuillermin  13   14 , Dan Casalaz  15 , Nigel Curtis  1   2   16 , Nicole L Messina  1   2 ; Melbourne Infant Study: BCG for Allergy and Infection Reduction (MIS BAIR) Group
Affiliations
Clinical Trial

Neonatal BCG vaccination to prevent asthma: Results from the MIS BAIR randomized controlled trial

Laure F Pittet et al. Pediatr Allergy Immunol. 2025 Jun.

Abstract

Background: Asthma has a significant impact worldwide, but prevention strategies remain limited. We aimed to evaluate the efficacy of neonatal BCG vaccination in preventing asthma by modulating early-life immunity.

Methods: The Melbourne Infant Study: BCG for Allergy and Infection Reduction (MIS BAIR) was a phase 3 multicentre randomized controlled trial in Victoria, Australia. Infants were randomly assigned to receive the BCG-Denmark vaccine or no intervention within 10 days of birth. The incidence of asthma at 5 years of age was estimated using the International Study of Asthma and Allergies in Childhood questions.

Clinicaltrial: gov (NCT01906853).

Results: A total of 1272 infants were randomized. The adjusted incidence of asthma was 14.4% in the BCG group compared to 16.0% in the control group (adjusted risk difference [aRD] -1.7 percentage points; 95%CI -7.4, 3.9). Secondary outcomes, including severe asthma and use of preventer medication, showed similar trends, with an aRD of -3.9 (95%CI -7.7, 0.0), and -5.6 (95%CI -10.9, -0.4), respectively, favoring the BCG group. Among participants with one or both parents asthmatic, the rate of asthma was also lower in the BCG group (17.6%) compared with the control group (24.7%; aRD -7.2; 95%CI -15.9, 1.5), although a test for interaction was not significant (p = .07).

Conclusions: While the point estimates suggested BCG vaccination might protect against asthma, the wide uncertainty around the estimates means further studies with larger sample sizes are needed to evaluate the long-term benefits of BCG vaccination beyond its primary indication.

Keywords: BCG vaccine (Mycobacterium bovis); asthma; prevention; vaccine non‐specific off‐target effects; wheeze.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
CONSORT diagram. BCG, bacille Calmette‐Guérin.
FIGURE 2
FIGURE 2
Difference in presence and severity of asthma between BCG and control groups, assessed at 5 years of age. Left: Bars represent the proportion of participants fulfilling the criteria for the primary and secondary outcomes. Right: Squares represent adjusted risk differences for the multiple imputation models, with error bars depicting 95% CI. Allergic sensitization was defined as positive skin prick test at the 1‐year visit (post hoc subgroup analysis).
FIGURE 3
FIGURE 3
Subgroup analysis of incidence of asthma at 5 years of age. Bars represent the proportion of participants fulfilling the criteria for the primary outcome of asthma in prespecified subgroups; error bars depict 95% CI. The vertical dotted lines represent the proportion of participants with asthma in the whole BCG (blue) and control (gray) groups. p‐values are for the interaction term (BCG status by variable). Allergic sensitisation was defined as a positive skin prick test at the 1‐year visit (post hoc subgroup analysis).
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