More tobacco smoke children breath in, the more likely they were to develop a serious infection..

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December 12, 2010 - Epidemiologic studies have observed an association between secondhand smoke (SHS, passive smoking, second hand smoke, involuntary smoking, sidestream smoke) exposure and pediatric invasive bacterial disease (IBD) but the evidence has not been systematically reviewed.

Chien-Chang Lee of the Harvard School of Public Health in Boston reviewed other studies to find a clear dose relationship -- the more tobacco smoke children breathed in, the more likely they were to develop a serious infection.

PAPER: Association of Secondhand Smoke Exposure with Pediatric Invasive Bacterial Disease and Bacterial Carriage: A Systematic Review and Meta-analysis, Chien-Chang Lee1,2, Nicole A. Middaugh1, Stephen R. C. Howie3, Majid Ezzati4, published in the Public Library of Science journal PLoS Medicine, Abstract, Full Text, Editors' Summary..

Study found that children exposed to second-hand smoke were twice as likely to get serious infections called invasive meningococcal disease than children not exposed.
Children who breathed in smoke were also more likely to carry other bacteria such a Streptococcus pneumoniae, they found.

Chien-Chang Lee: When considered together with evidence from direct smoking and biological mechanisms, our systematic review and meta-analysis indicates that SHS exposure may be associated with invasive meningococcal disease. The epidemiologic evidence is currently insufficient to show an association between SHS and invasive Hib disease or pneumococcal disease. Because the burden of IBD is highest in developing countries where SHS is increasing, there is a need for high-quality studies to confirm these results, and for interventions to reduce exposure of children to SHS.

from Editor's Summary: Children are particularly vulnerable to the effects of SHS exposure (also known as passive smoking) because they are still developing physically. In addition, children have little control over their indoor environment and thus can be heavily exposed to SHS. Exposure to SHS increases the risk of ear infections, asthma, respiratory symptoms (coughing, sneezing, and breathlessness), and lung infections such as pneumonia and bronchitis in young children and the risk of sudden infant death syndrome during the first year of life.

Reference: in part Maggie Fox, Health and Science Editor Reuters, 12/7/2010..