Vaccinating african children against pneumococcal disease saves lives
The World Health Organization (WHO) today welcomed the results of a pneumococcal conjugate vaccine trial conducted in The Gambia which are published in the Lancet this week, and comments as follows:
Dr LEE Jong-wook, Director-General, WHO, declared:
"The results of this vaccine trial hold great promise for improving health and saving lives in resource-poor populations. The international community's task now is to continue to work together productively to make the pneumococcal conjugate vaccine widely available to children in Africa, as lives are lost every minute to pneumococcal disease. Immunizing children with pneumococcal conjugate vaccine in developing countries will be a critical intervention towards achieving a two-thirds reduction in the under-five mortality rate, a Millennium Development Goal."
Dr Felicity Cutts, principal investigator of the trial who is currently based at WHO, said:
"The trial results are highly positive and promising, and provide us with a clearer picture of the pneumococcal disease burden in Africa. The trial confirms that pneumococcal pneumonia, meningitis, and sepsis are major causes of death and serious illness among African infants and young children. Most importantly, it demonstrates that pneumococcal vaccination can prevent many of these serious infections even in a rural African setting. This is great news for children and parents in rural areas everywhere."
A similar vaccine has had a dramatic impact on reducing pneumococcal disease in the United States. The Gambia vaccine trial has now clearly demonstrated that a significant proportion of illness, disability and death in African children can be averted through vaccination against this disease, a leading killer, especially of young children in developing countries.
Dr Thomas Cherian, Team Coordinator in the WHO Initiative for Vaccine Research stated:
"Experience has shown that in areas where health systems are unable to provide hard to reach, rural populations with round-the-clock access to high-quality curative care, immunization can be delivered through outreach services to great benefit. The pneumococcal vaccine will therefore be particularly important to save lives in the most disadvantaged populations."
The trial was supported by a broad coalition of international partners including the WHO Initiative for Vaccine Research, the National Institute of Allergy and Infectious Diseases/National Institutes of Health; the British Medical Research Council/United Kingdom working with The Gambia Government; the London School of Hygiene and Tropical Medicine; the U.S. Agency for International Development; the Centers for Disease Control and Prevention of the United States Health and Human Services Department; Wyeth-Lederle Vaccines; the Program for Appropriate Technology in Health (PATH) Children’s Vaccine Program, as well as WHO.
Pneumonia is estimated to kill nearly two million children every year; it is responsible for approximately 18% of the more than ten million annual childhood deaths worldwide. Pneumococcal disease is caused by infection with the Streptococcus pneumoniae bacterium. Such infections cause several clinical diseases including sepsis (a severe illness caused by overwhelming infection of the bloodstream by toxin-producing bacteria), meningitis (an infection of the fluid of a person's spinal cord and the fluid that surrounds the brain) and pneumonia (an inflammation of the lung caused by infection with bacteria, viruses, or other organisms). This bacterium is also a common cause of ear infections, which can lead to deafness if they are not treated properly. In the Gambia and other African countries, rates of invasive pneumococcal disease (severe forms of the disease, where bacteria are isolated from blood, spinal fluid or another site in the body where bacteria are not usually found), are up to ten times higher than in industrialized countries and the disease is a major cause of hospital admissions and deaths. WHO estimates that between 700 000 and 1 million children under five die from pneumococcal diseases each year.
A randomized, controlled, double-blind trial of a pneumococcal conjugate (made from linking purified polysaccharides or complex sugars from the coat of a disease-causing bacterium to a protein carrier) vaccine took place in eastern Gambia starting in August 2000. 17 437 children aged 6-51 weeks were enrolled in the study. Those 8719 children in the control group received a diphtheria-tetanus-pertussis-Haemophilus influenzae serotype b vaccine. 8718 children received pneumococcal conjugate vaccine, mixed with the tetravalent vaccine received by the control group.
Results of the trial indicated that in the group of children who received pneumococcal conjugate vaccine, there were:
- 37% fewer cases of pneumonia (as confirmed by chest X-ray);
- 15% fewer hospital admissions
- 16% reduction in overall mortality; and
- half the rate of laboratory-confirmed pneumococcal pneumonia, meningitis and septicaemia.
Moreover, the vaccine was 77% effective in preventing infections caused by nine serotypes (strains) of pneumococcal bacteria whose sugar capsules make up the vaccine.
In sum, in this rural African setting, pneumococcal conjugate vaccine was shown in this trial to be highly effective against pneumonia and invasive pneumococcal disease and it can substantially reduce admissions and improve child survival.
Full details of the trial are available in a paper published in the Lancet on 26 March 2005 by Dr Felicity T. Cutts et al. entitled Efficacy of nine-valent pneumococcal conjugate vaccine against pneumonia and invasive pneumococcal disease in the Gambia: randomised, double-blind, placebo-controlled trial. The authors of the paper conclude that pneumococcal conjugate vaccines should be made available as soon as possible to African infants.