New research has found pneumococcal vaccinations in Fiji have halved the number of children carrying the dangerous bacteria.
The naturally occurring bacteria is a common cause of meningitis, blood poisoning and pneumonia in children, and the World Health Organisation recommends vaccinating children in the Pacific against it.
Fiji became one of the few Pacific Island nations to introduce the vaccine into its national immunisation programme.
Eileen Dunn from Australia's Murdoch Children's Research Institute said the vaccine was expensive for a country like Fiji but it was subsidised by the international community.
"In Fiji there is a high burden of pneumonia. Our recent study found that the vaccine reduced the bacteria not only in vaccinated children but also in other age groups, Dr Dunne said.
"So this is an important finding demonstrating that by vaccinating young children we can also prevent the spread of disease to other age groups in the population."