The bacterial lysate OM-85 did not prevent wheezing illness in high-risk infants

Design

Randomised, double-blind, placebo-controlled trial

Population

822 children aged 6–18 months at high risk of asthma

Primary outcome

Time to first wheezing lower respiratory illness over 36 months off drug

Effect

21% vs 18%, HR 1.16 (95% CI 0.82 to 1.64)

ORBEX randomised 822 children aged 6 to 18 months at high risk of asthma (atopic dermatitis, or a parent or sibling with asthma) at 11 US sites to OM-85 3.5 mg or placebo, 10 days a month for 24 months. The primary outcome was time to a first wheezing lower respiratory illness over a further 36 months off treatment.

During that period, 21% of the OM-85 group and 18% of the placebo group had a wheezing illness (HR 1.16, 0.82 to 1.64). Adverse events did not differ. The authors conclude bacterial lysates do not work for primary prevention of preschool wheeze.

OM-85 is sold in many countries and prescribed to prevent recurrent respiratory infections and wheeze in children. This trial tested prevention of a first wheezing illness, which is the use parents are most often offered. The result argues against starting it for that purpose.

• Do not start OM-85 to prevent wheezing in at-risk infants
• Explain to parents that a large placebo-controlled trial found no benefit
• Focus prevention on smoke-free homes and routine vaccination
• Treat wheezing episodes as usual, by guideline

Why it matters

It removes the evidence basis for a commonly offered preventive product in young children.

Don't overread it

It tested primary prevention in infants; it does not address OM-85 for children who already have recurrent wheeze.

The statistics, in plain English

A hazard ratio of 1.16 points slightly the wrong way, and the interval (0.82 to 1.64) means the data are compatible with at best an 18% benefit. So a meaningful protective effect is unlikely. About 28% of children did not complete the observation period, which weakens precision but would have to be heavily biased to hide a real benefit.

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