Indonesia-based study shows higher incidence of Haemophilus Influenzae Type b than previously known

Seattle, December 31, 2004—A five-year study in Indonesia finds that Haemophilus influenzae type b (Hib), a major cause of pneumonia and meningitis in infants, may be more of a health problem in Asia than previously thought. Prior to this study on the island of Lombok, nearly all Hib research in Asia had been based on microbiology and had concluded that Asia had a low burden of Hib disease. Experts did not know if this was because the disease really was uncommon or if traditional microbiology was not detecting it.

This study took a novel approach in which researchers used a vaccine to measure the burden of disease by comparing the incidence of disease among unimmunized and immunized children in the same population. The study involved a joint effort by scientists and public health specialists from the Indonesian Ministry of Health; PATH, an international nonprofit organization based in Seattle, Washington, USA; and the Association Pour l’Aide à la Médicine Préventive (AMP), a nongovernmental public health organization based in Paris, France. Findings of their report were published in this week’s issue of the British medical journal, The Lancet.

“The study team found that the burden of Hib disease in Asia may be much higher than expected, as high as anywhere else in the world outside of a few special populations,” according to David Mercer, an investigator for PATH’s Children’s Vaccine Program, one of the partners who conducted the study. The rate of vaccine-preventable meningitis detected by the team’s vaccine probe study was ten times greater than the rate detected in the laboratory, and the incidence of pneumonia prevented was also found to be much higher than anticipated.

The rate of confirmed meningitis cases in immunized children was half the rate of those who did not receive the vaccine. In addition, the percentage of death from meningitis in immunized children was almost half that of unimmunized children. The vaccine’s results for preventing pneumonia were more measured. The study found that Hib vaccine prevented a relatively small proportion of clinical cases of pneumonia, indicating that most pneumonia on Lombok is caused not by Hib but by other organisms. However, because pneumonia is very common on Lombok, the small proportion (less than 5 percent) prevented by the vaccine represented a very large number of cases.

Overall, the study estimated that one in 33 unimmunized infants on Lombok contracts Hib meningitis or pneumonia before turning two years of age. Given the large number of cases of disease preventable by this vaccine, and in particular its potential impact on meningitis, the study members suggest consideration be given to inclusion of Hib vaccine in routine infant immunization programs in Asia. Hib vaccine is used as part of routine childhood immunization in more than 30 countries in the world.

The research project was supported by the Government of France, the Mérieux Foundation, Aventis Pasteur through AMP, Aventis Pasteur for the vaccine donation, PATH’s Children’s Vaccine Program, and the United States Agency for International Development.