Routine Vaccination Could Eliminate Hib Disease in Children in Developing Countries

Routine immunization against a bacterial microorganism that can cause meningitis and pneumonia should be introduced for children in developing countries, suggests a report published in this weeks issue of The Lancet. The study shows that disease caused by Hemophilus influenza type b (Hib) has been virtually eliminated from children in The Gambia after the introduction of a nationwide vaccination program.

In 1997, a trial in over 40 000 infants in The Gambia found a Hib vaccine* was 95 percent effective against the diseases associated with Hib. However, the vaccines effectiveness was tested under optimum trial conditions. In routine use in developing countries, suboptimum storage and transport conditions can reduce a vaccines effectiveness.

Richard Adegbola of the Medical Research Council in the United Kingdom and colleagues investigated the effectiveness of the Hib vaccine when delivered via The Gambias existing expanded program on immunization (EPI). Routine immunization of infants in the Gambia with the Hib vaccine began in May 1997. The researchers monitored children in the western region of The Gambia for Hib disease from May 1997 to April 2002. A total of 5984 children were investigated as possible cases of Hib infection. When a case of the disease was confirmed a researcher recorded the vaccination status of the child. The investigators found that after the introduction of routine Hib immunization, the annual incidence rate of meningitis in infants in The Gambia dropped sharply from over 200 per 100 000 to 21 per 100 000 in the first 2 years of vaccination. The incidence declined further to 0 per 100 000 in the fifth year after the introduction of routine immunization. The authors note that the reduction was achieved despite difficulties with a regular supply of vaccine. No cases of Hib disease have been identified in the western region since 2002.

Adegbola states, Hib disease has been eliminated in developed countries for two decades, but many developing countries are still reluctant to introduce routine vaccination due to the lack of available information on how effective it is, especially when vaccine supplies might be erratic. Our study shows that despite an erratic vaccine supply, elimination of Hib disease is possible. We hope other countries in sub-Saharan Africa will now be encouraged to also adopt routine Hib vaccination programs as this could help achieve the United Nations Millenium Development goal of decreasing childhood deaths by two-thirds by the year 2015.

In an accompanying comment, John Clemens of the International Vaccine Institute in Seoul, Korea states that policy-makers will need information on the burden of Hib disease and the costs and feasibility of a Hib immunization program in other developing countries before committing to vaccine introduction.

* Haemophilus influenzae type b (Hib) polysaccharide-tetanus toxoid conjugate vaccine

Source: The Lancet