BCG asthma effects are lost in adolescence

By Stephanie Leveene, medwireNews Reporter

Any beneficial effects of the neonatal Bacillus Calmette–Guérin (BCG) vaccine on childhood asthma symptoms and outcomes are likely to be transient, disappearing by adolescence, show follow-up findings from the Manchester Community Asthma Study (MANCAS).

“BCG vaccination does not protect against the development of allergic sensitization or other allergic disorders,” state Mary Linehan (University of Manchester, UK) and colleagues in the Journal of Allergy and Clinical Immunology.

The original MANCAS results found that children who received a standard dose of the neonatal BCG vaccine (<12 weeks of age) had a reduced risk for wheezing and improved related outcomes at age 6 to 11 years.

In this follow-up retrospective cohort study, MANCAS 2, Linehan and colleagues sought out whether these beneficial effects were maintained over the long term. Questionnaires were sent out to eligible children aged 13 to 17 years, including those who did not receive the BCG vaccine during the original study period, and responses were linked to immunization records.

Among 1608 respondents, those who received the vaccine had similar rates of wheezing (15.8 vs 14.3%, respectively) and hay fever/eczema (44.4 vs 46.0%) to those who did not receive the vaccine. This was the case even when both measures were stratified for neonatal BCG vaccine, postnatal BCG vaccine (>12 weeks of age), and high-dose vaccine (due to hospital error).

The updated meta-analysis estimated overall odds ratios of 0.95 for asthma risk and 1.05 for sensitization risk in those who were vaccinated versus those who were not. For allergy in general, the estimated odds ratio was 0.94.

The combined data from the MANCAS 2 questionnaire and updated meta-analysis “provide further evidence that any benefits associated with BCG vaccination on asthma outcomes are likely to be transient and unlikely to be mediated through reducing the risk of atopy,” concludes the team.

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