Vaccine against pneumonia and invasive pneumococcal disease shows promise

A vaccine against pneumonia and invasive pneumococcal disease, a severe form of bacterial infection, can substantially reduce hospital admissions and improve the survival of children in developing countries, concludes a trial published in this week’s issue of The Lancet.

The authors believe the vaccine should be made available to children in Africa, where rates of severe invasive pneumococcal disease are up to ten times higher than in industrialised countries.

Pneumonia causes an estimated 19% of the 10 million childhood deaths worldwide annually. The bacterium Streptococcus pneumoniae is responsible for up to half of all cases of severe childhood pneumonia in developing countries. It also causes serious bloodstream infections, meningitis, and otitis media (inflammation of the middle ear).

Felicity Cutts (Medical Research Council, UK and WHO) and colleagues recruited children aged 6–51 weeks in The Gambia from August 2000 to February 2003. Children were randomly assigned to receive either, three doses of diphtheria-tetanus-pertussis—Haemophilus influenzae serotype b vaccine as a control (8719), or three doses of this tetravalent vaccine mixed with a nine-valent pneumococcal conjugate vaccine (8718), with intervals of at least 25 days between doses. 333 of the 8189 children given the pneumococcal vaccine had an episode of pneumonia confirmed by chest x-ray compared with 513 of 8151 in the control group. The vaccine reduced the first episode of pneumonia diagnosed by chest x-ray by 37% and reduced admissions to hospital by 15%. Disease caused by the types of pneumococcus bacteria in the vaccine was lowered by 77% and overall child mortality by 16%. The vaccine also had a good safety profile.

Professor Cutts comments: “The trial results are highly promising, and provide us with a clearer picture of the pneumococcal disease burden in Africa. In the control group, 65% of invasive disease episodes were of serotypes contained in the nine-valent trial vaccine, and 48% were of serotypes in the licensed seven-valent vaccine. Vaccines containing more serotypes could have an even greater effect. Identification of means to make pneumococcal conjugate vaccines available as soon as possible to children who need them most is extremely important.”

In an accompanying commentary, Marilla Lucero and Gail Williams, write that studies on a seven-valent (7PCV) and a nine-valent pneumococcal conjugate-vaccine (9PCV) in California and South Africa, respectively found similar results on the impact of the vaccine against pneumonia confirmed by chest x-ray. However, there is some uncertainty about the comparability of results because of different methods used in reading radiographs. The Gambian trial had a higher reduction of incidence of radiological pneumonia and is the first to show a reduction in hospital admissions and overall child mortality.