Authors' conclusions: secondhand smoke may be associated with invasive meningococcal disease, although that should be confirmed by high quality studies. The possible risk detected and the increasing secondhand smoking in developing countries, where invasive disease is more frequent, make it necessary to favor interventions for reducing children exposure to tobacco.
Reviewers' commentary: passive smoking showed a significant association with meningococcal invasive disease and with the meningococcus and pneumococcus carrier state. However, it is not clear that this association is causal and it may reflect the effect of other environmental factors associated with lower socioeconomic status. Prospective studies are required with an appropriate adjustment for other risk factors to confirm this association.