Response of 7- to 15-month-old infants to sequential immunization with Haemophilus influenzae type b-CRM197 conjugate and polysaccharide vaccines

Article Abstract:

Infection with the bacteria Haemophilus influenzae most often affects the respiratory system, but it also causes influenzal meningitis, or inflammation of the membranes of the brain and spinal cord; conjunctivitis, or inflammation of the membrane lining the eye; and septicemia, or bacterial infection of the blood. H. influenzae infection can be prevented by a vaccine that promotes the production of antibodies, or immune proteins, specifically directed against H. influenzae. The original vaccine, called H. influenzae type b polysaccharide (HbPs) vaccine, was not very effective in boosting immunity in infants less than 18 to 24 months of age. Conjugate vaccines consist of a protein and saccharide (sugar) component of the bacteria, and have two major functions: to promote the production of antibodies directed against H. influenzae and to prime, or prepare, the immune system so that subsequent exposure to H. influenzae can activate the production of antibody. The H. influenzae type b oligosaccharide-CRM 197 conjugate vaccine (HbOC) is a newly licensed conjugate vaccine. The effects of the HbOC and HbPs vaccines on the immune responses of infants aged 7 to 15 months were assessed. The study involved 71 infants who received three doses of the HbOC vaccine, 47 who were given two doses of HbOC vaccine followed by one dose of HbPs, and 53 who received one dose of HbOC vaccine followed by two doses of the HbPs vaccine. The infants were vaccinated at birth, two months and six months. A second dose of the HbPs vaccine caused a smaller increase in antibody levels than the HbOC vaccine. Furthermore, infants given two doses of HbOC had large and similar increases in antibody levels one and six months after vaccination. These findings show that the conjugated HbOC vaccine is effective in causing the production of antibodies to levels that protect against H. influenza infection and prime the immune system for subsequent exposure. The HbPs vaccine can be given as a booster immunization. (Consumer Summary produced by Reliance Medical Information, Inc.)

Research, Measurement, Antibodies

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Protective efficacy of Haemophilus influenzae type b polysaccharide-diphtheria toxoid-conjugate vaccine

Article Abstract:

The relative efficacy of two vaccines was assessed for use against invasive Haemophilus influenzae type b infection in two groups of vaccinated children. Data used were derived from reports of spontaneous cases of Haemophilus influenzae type b disease that were reported to the Food and Drug Administration (FDA) Spontaneous Reporting System, a computerized database that contains information on adverse drug episodes reported by health professionals and pharmaceutical manufacturers. Additional data were obtained from investigators at Washington University School of Medicine, St. Louis, MO. The two vaccines examined were H influenzae type b polysaccharide (PRP) and PRP-diphtheria toxoid-conjugate (PRP-D) vaccine. H influenzae type b disease results in respiratory infection. It was previously considered to be the cause of influenza (flu), but is now believed to be a primary or secondary invader. The children were followed-up for 13 months after receiving PRP or PRP-D vaccine. A total of 127 cases of invasive H influenzae were reported in the group given the PRP vaccination; 17 cases were noted in the PRP-D group. The results of the data were limited by a number of variables within the subject population groups. The proportion of H influenzae cases that occurred 14 days or more after vaccination was significantly greater for the PRP vaccine group (106 of 127 cases) than for the group who received PRP-D vaccine (7 of 17 cases). Only seven failures occurred with the PRP-D vaccine; this was fewer than the 86 percent that was expected. The findings demonstrated that the PRP-D vaccine was more effective than the PRP vaccine in preventing infection by H. influenzae type b 14 days or more after immunization. (Consumer Summary produced by Reliance Medical Information, Inc.)

Hemophilus influenzae, Haemophilus influenzae

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Immunogenicity of Haemophilus influenzae type b polysaccharide-tetanus toxoid conjugate vaccine in infants

Article Abstract:

A multicenter, randomized immunogenicity trial involving 485 infants from private pediatric practices in five geographic areas was carried out to compare the safety and immunogenicity of three investigational lots of Haemophilus influenzae type b polysaccharide-tetanus toxoid (PRP-T) conjugate vaccine. Each of the infants was vaccinated at 2, 4 and 6 months of age with one of three lots of PRP-T. All the infants received oral polio, DTP and Hib conjugate on the same visit, but adverse events did not surpass those expected from DTP vaccine alone. To compare the immunogenicity of the three lots of PRP-T and the HbOC vaccine, the data from the five study locations were combined. They showed that PRP-T and HbOC were immunologically similar. PRP-T was subsequently licensed in the U.S., France and other European countries.

Safety and security measures, Hib vaccines

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