Given the high prevalence of
chronic obstructive pulmonary disease (
COPD), the impact of exacerbations on quality of life, and the costs incurred, effective ways for the prevention of exacerbations, and for reductions in the severity and duration of
COPD symptoms are needed. Bacterial immunostimulation has been advocated as a management strategy in
COPD for the purposes of preventing acute exacerbations. In particular, it suggests that the use of oral multicomponent
vaccines may reduce the severity and duration of acute episodes. The way in which
bacterial extracts may exert their effects is not fully understood although a number of possible specific mechanisms have been suggested. Given the high prevalence of
COPD worldwide and the high cost of acute exacerbations, some cost-effectiveness analyses suggest that bacterial
immunostimulants may become a key
element in the improved control of this condition. Nonetheless, larger and longer clinical trials are needed to investigate efficacy before oral vaccination could be recommended as part of the routine clinical management of
COPD, mainly in advanced
COPD. It remains also to be investigated whether this protective effect may be additive to the other treatments. In any case, it is well known that for Streptococcus pneumoniae, non-typable Haemophilus influenzae and Moraxella catarrhalis,
recurrent infections occur because of strain heterogeneity. Therefore, a single or even multiple strain
vaccine with a killed whole cell formulation is possibly not the ideal
vaccine. Moreover, the method of inactivation can affect the immunogenicity of essential
antigens through denaturation. For this reason, the efficacy of bacterial
immunostimulants should not only be assessed but also compared.