Acute respiratory infections (ARI) are the most frequent diseases suffered by human beings. A child living in an urban area may suffer between four and nine episodes of ARI during his first year of life, and between one and 5 per year in the four subsequent years. Incidence of ARI is similar in industrialized and developing countries, but with a higher relative severity of lower ARI, mainly pneumonia. This article reviews the current situation and expected developments of three of the vaccines that are likely to have greater impact in the morbidity and mortality of lower ARI, that is, Haemophilus Influenzae type S, Streptococcus Pneumoniae, and respiratory Syncytial Virus.
