In Tari, in the southern highlands of Papua New Guinea, each child experienced, on average, two acute lower respiratory tract infections (ALRTI) between birth and age 5 years. The yearly mortality rate from ALRTI was 30 per 1000 in infants, and 4 per 1000 in children aged between 1 and 4 years. A double-blind trial of a 14-valent pneumococcal polysaccharide vaccine was carried out on 871 children from this community who were aged between 6 months and 5 years. Morbidity from ALRTI was lower (by 37%) in children given the vaccine provided they were at least 17 months of age at the time of immunisation. There were 8 deaths from ALRTI in the placebo group, but only 1 death in the vaccine group.