Immunising children may protect whole African villages from pneumococcal disease

Vaccinating young children in Africa against pneumococcus may help protect their entire communities from deadly infections this bacterium can cause, a new study coauthored by a University of Otago researcher suggests.

Invasive pneumococcal disease can strike all ages but takes its grimmest toll on the young, annually killing an estimated 800,000 children under-five worldwide through illnesses such as pneumonia, blood infection and meningitis.

In a randomised controlled trial involving 21 villages in rural Gambia, researchers showed that vaccinating young children reduced nasal carriage of the types of pneumococcal bacterium that the PCV-7 vaccine targeted; not only in the vaccinated children, but also in vaccinated and non-vaccinated older children and adults. Otago’s Professor Philip Hill led the field aspects of the study before taking up his position at the University.

Professor Hill, Director of the University’s Centre for International Health, says that previously there were concerns that achieving this kind of ‘herd effect’ through immunising infants against pneumococcus would be much more difficult in Africa than in other regions.

“We have now shown for the first time that, despite the greater prevalence of pneumococcal carriage and a high level of infection transmission compared to other parts of the world, it may be feasible to protect entire communities in Africa from pneumococcal disease through vaccinating young children alone,” he says.

The study, which appears in this week’s issue of PLoS Medicine, also showed that vaccinating whole communities did not result in a community-wide increase in carriage of non-vaccine serotype pneumococci — other types of pneumococci that are not included in the vaccine — in the two-year period after vaccination.

“This is an encouraging finding, as the fear always is that non-vaccine pneumococci types will rush in to replace those to which people are now immune. This would lead to reduced benefits from what is an expensive vaccination programme for a low-income country.”

Professor Hill and colleagues at the Medical Research Council (MRC) Unit in The Gambia will continue to study the effectiveness of PCV-7 vaccine and other newer vaccines which target a wider range of pneumococci types. Recently the Unit was awarded a US $7M grant over four years from the Bill & Melinda Gates Foundation to support this work in rural Gambia.The PLoS Medicine study was led by researchers from the MRC Unit in collaboration with the London School of Hygiene & Tropical Medicine.

A copy of the paper is available on the PLOS Medicine website.