Limited efficacy of a Haemophilus influenzae type b conjugate vaccine in Alaska native infants

Article Abstract:

Haemophilus influenzae type b is a bacteria that can cause serious illnesses, such as bacteremia (bacterial infection of the blood), meningitis, septic arthritis, pneumonia, and death in young children. Most of the 20,000 people who contract this infection each year in the United States are children under 5 years of age. Several groups of Native North Americans, including Indians, Eskimos, and Aleuts, have been found to have a significantly increased rate of infection and complications from Haemophilus influenzae. While there have been many theories as to the underlying reasons for the elevated risk of Haemophilus influenzae type b infections in these groups, there have been no conclusive studies on the subject. As antibiotic therapy is not expected to reduce the illness or deaths from this bacteria, the major means of reducing the virulence of the disease is by immunization. A vaccine which recognizes specific sugars on the bacterial coat has been developed, but it is not very effective against the bacteria in children under 18 months of age, which is the population at greatest risk. A new vaccine which is produced against a carbohydrate-protein viral extract coupled to diphtheria toxin has been found to be more effective in certain groups of children. This study evaluates the efficacy of this polysaccharide-diphtheria toxoid conjugate vaccine in protecting Alaska Native infants from Haemophilus influenzae type b. A total of 2,102 infants were either given the vaccine at 2, 4 and 6 months of age or they were given an inactive placebo injection. The rate of Hemophilus influenzae infection in both groups was recorded, and no difference in infection rate was found between the two groups. Despite studies in other groups showing the great effectiveness of this vaccine in preventing disease in infants, the current study found no evidence of protection in this North American population. Blood antibody levels in response to the vaccine, although higher than in the control group, were inadequate. This failure to produce enough antibodies paralleled the inability of the vaccine to protect these children. The results of this study fail to confirm the significant protection of young children which has been previously reported in European groups. Possible explanations include racial differences, experimental design, degree of exposure to the bacteria, social differences, and different strains of bacteria. (Consumer Summary produced by Reliance Medical Information, Inc.)

Alaska

---

The efficacy in Navajo infants of a conjugate vaccine consisting of Haemophilus influenzae type b polysaccharide and Neisseria meningitidis outer-membrane protein complex

Article Abstract:

Infection by Haemophilus influenzae type b bacteria can lead to a variety of serious complications, including meningitis, in which the membranes that surround the brain and spinal cord become inflamed. Some population groups, including certain Native American tribes, have infection rates several times higher than the general population. To evaluate the effectiveness of a new vaccine among Navajo infants, a controlled study was carried out. Infants aged between 42 and 90 days were randomly assigned to receive either the vaccine (2,588 subjects), a conjugate of H. influenzae type b capsular polysaccharide and parts of the outer-membrane protein complex (OMPC) of Neisseria meningitidis serogroup B, or a placebo (2,602 subjects), an inactive substance. Second injections were given between the ages of 70 and 146 days. Blood samples were obtained at different points during the study and analyzed to determine the infants' levels (titers) of antibodies against H. influenzae; the safety and efficacy of the vaccine were also monitored. The study began in July 1988; by August 1990, after 23 cases of H. influenzae infection had occurred, it was decided to stop the study. The group that had received the vaccine had far fewer cases than the placebo group (1 case versus 22 cases) by the age of 18 months. Thirteen of the 22 placebo cases developed meningitis. No infections occurred in the vaccine group between the first and second doses of vaccine; eight occurred in the placebo group. Antibody levels did not increase noticeably after the second vaccination, but the vaccine was effective up until 18 months of age. The overall efficacy of the H. influenzae type b OMPC vaccine was more than 90 percent in this population. This was much higher than the efficacy reported for another conjugate vaccine in another study of Native Americans in Alaska. Use of this vaccine should eliminate H. influenzae type b infection. (Consumer Summary produced by Reliance Medical Information, Inc.)

Innovations, Navajos, Hib vaccines

---

Impaired antibody response to Haemophilus influenzae type b polysaccharide and low IgG2 and IgG4 concentrations in Apache children

Article Abstract:

Certain groups of native American children are at high risk for invasive bacterial infections. Infections with the bacteria Haemophilus influenzae type b and Streptococcus pneumoniae are considered 10 to 50 times more common in Native American children than in white children. Additionally, the rate of life-threatening complications of Haemophilus influenzae infection is also considerably higher in the Native American groups. Native Americans also have a higher rate of ear infection, intestinal infections, and pneumonia. The underlying reasons for this difference in infection rate when compared with white North American populations are not well understood, and some have speculated that this trait may be related to a difference in the immune system of these individuals. The present report compares the antibody levels of Apache and white children of similar ages before and after immunization with a vaccine produced against a polysaccharide (a carbohydrate, or complex sugar) extracted from the viral envelop of Hemophilus influenzae. The level of protective antibody against Hemophilus influenzae in Apache children following immunization was found to be approximately 10 times lower than the blood level of this antibody in white children. The level of tetanus antibody, produced by a different class of vaccine, was not significantly lower in Apache children, indicating that vaccines can lead to the production of antibodies in these children. The results show that Apache children, while able to adequately produce anti-tetanus antibody, have a significantly decreased ability to produce antibodies in response to immunization with Hemophilus influenzae type b polysaccharide vaccine. This inability, and the concomitant difference in the immune system of this group, may be related to the increased rate of infection in this population. (Consumer Summary produced by Reliance Medical Information, Inc.)

Social aspects

Similar abstracts:

• Abstracts: Work continues on extending protection against Haemophilus influenzae to very young infants. Clearing the Way for New Combination Vaccine Use
• Abstracts: Measles incidence, vaccine efficacy, and mortality in two urban African areas with high vaccination coverage. Patterns of transmission and severity of measles infection: a reanalysis of data from the Machakos area, Kenya
• Abstracts: Safety and efficacy of oral flecainide therapy in patients with atrioventricular re-entrant tachycardia. Inefficacy and proarrhythmic effects of flecainide and encainide for sustained ventricular tachycardia and ventricular fibrillation
• Abstracts: A randomized, prospective field trial of a conjugate vaccine in the protection of infants and young children against invasive Haemophilus influenzae type b disease

This website is not affiliated with document authors or copyright owners. This page is provided for informational purposes only. Unintentional errors are possible.