Acute respiratory infections (ARI) cause more than four million childhood deaths each year in developing countries. In addition to standard case management, vaccines have a great potential for reducing these deaths. Immunization against measles and pertussis, already reaching more than 70% of infants in developing countries, contributes to the prevention of more than one million childhood deaths. New conjugate vaccines against Haemophilus influenzae type b, if shown to be effective against pneumonia in developing countries, could reduce acute lower respiratory infection (ALRI) deaths by 4%. A further 10% reduction could be obtained by the availability of an effective conjugate vaccine against Streptococcus pneumoniae. A safe vaccine against respiratory syncytial virus could also prevent 10% of ALRI deaths. The potential role of other bacterial and viral vaccines needs to be clarified.