New vaccines against Haemophilus influenzae type b

Feasibility study of the immunogenicity and safety of a novel DTPw/Hib (PRP-T) Brazilian combination compared to a licensed vaccine in healthy children at 2, 4, and 6 months of age

Vaccination of infants with conjugated Haemophilus influenzae type b (Hib) vaccines has been proven to reduce Hib meningitis by 95% and pneumoniae by 20%. The routine use of Hib vaccine is facilitated by the introduction of combination vaccines into the EPI (Expanded Plan of Immunization). The objective of this study was to compare the immunogenicity and reactogenicity of an extemporaneously mixed DTPw/Hib (diphtheria-tetanus-whole cell pertussis) combination, using the technology of two Brazilian manufacturers, against a licensed DTPw/Hib European combination in 108 infants vaccinated at 2, 4 and 6 months according to the local national schedule. The Brazilian combination was highly immunogenic with Hib seroprotection rates (anti-PRP > 0.15 mg /ml of 98% after 2 doses and 100% after 3). Also for tetanus and pertussis the new Brazilian combination was as immunogenic as the European counterpart, except the diphtheria seroprotection rates and titers were lower. There was also no clinically relevant difference in reactogenicity. If these feasibility results are confirmed, the Brazilian DTPw/Hib combination should help to boost the uptake of Hib vaccination in Brazil.

Immunization and the prevention of childhood diseases

Nursing has an important role in improving the incidence of childhood immunization. An understanding of the immunologic deficiencies of children, especially those younger than 5 years, demonstrates the need for this population-wide protection. Knowledge of the various products, their efficacy, schedule, side effects, and contraindications will assist the neonatal and pediatric nurse in coordinating immunizations and teaching parents about this important health priority for their children. Research is focusing on the development of combination vaccines and products for infectious diseases that currently have difficult or nonexistent treatment.

Haemophilus influenzae type B epiglottitis after immunization with HbOC conjugate vaccine

INTRODUCTION

US Food and Drug Administration (USFDA) has licensed four Haemophilus influenzae type B (Hib) vaccines for use in children. Haemophilus influenzae type B is by far the most common pathogen in childhood epiglottitis and it is hoped that with the introduction of the Hib vaccine that a corresponding decrease in epiglottitis cases will be appreciated.

MATERIALS AND METHODS

A retrospective study of all children admitted with the diagnosis of epiglottitis for the 11-year period of 1982 to 1992 was conducted in order to determine the incidence of epiglottitis and Hib vaccine failure. Fifty-nine cases were included in the study by documentation of an inflamed epiglottis. The case of Hib epiglottitis in a 4-year-old child immunized with HbOC conjugate vaccine at 18 months of age is detailed.

RESULTS

A statistically significant decrease was found in the incidence of epiglottitis since introduction of the vaccines; however, the overall trend in decrease for the 11-year period was not statistically significant. Vaccination status was difficult to accurately document with only two cases of vaccine failure identified.

CONCLUSION

The incidence of Haemophilus influenzae type B epiglottitis at our regional Children's hospital has decreased since the introduction of the Hib vaccine. Reasons for vaccine failure are postulated.

Active immunization of children with leukemia and other malignancies

Active immunization against measles, Haemophilus influenza B, tetanus, diphtheria, hepatitis B, influenza, poliomyelitis, and, when indicated varicella and pneumococcus induces long-lasting immunologic protection in most healthy pediatric vaccine recipients. Among children receiving immunosuppressive therapy for cancer, possible early loss of specific immunity acquired from prior vaccination or disease, and likely diminished responsiveness to initial or booster vaccination must be considered. In addition, the safety of vaccine administration requires separate study in this population. Published evidence demonstrates preservation of vaccine-induced antibody titers against tetanus, diphtheria, poliomyelitis and (in children treated for lymphoma) pneumococcus. In contrast, prior immunity to varicella, influenza, and hepatitis B (when naturally acquired), and measles (acquired by vaccination) is compromised during and/or after antineoplastic therapy. Studies of immunologic protection acquired by prior vaccination against hepatitis B, varicella, and H influenza have not been published. The safety of administering toxoids and inactivated vaccines in this population is well documented. In contrast, morbidity must be expected if live attenuated vaccines (oral polio vaccine, attenuated measles vaccine or attenuated varicella vaccine) are administered to children receiving anti-cancer therapy. The risks of using live vaccines should be measured against demonstrable benefits in any vaccine program. The response to initial or booster immunizations against tetanus and diphtheria are similar to those in healthy children. For all other immunizations reviewed, responsiveness is diminished during periods of chemotherapy, more strikingly in children treated for leukemia than for solid tumors. Antibody responses to these vaccines range from slightly blunted (in the case of H influenza B) to marginal (influenza) or completely useless (pneumococcus and hepatitis B in children treated for leukemia).

Haemophilus influenzae type B conjugate vaccines

OBJECTIVE

To review the epidemiology of Haemophilus influenzae type b (Hib) disease, the first Hib vaccine and its limitations, the characteristics and clinical efficacy of the newer conjugate vaccines, and the current recommendations for administration of Hib vaccines.

DATA SOURCES

Pertinent literature was identified via a MEDLINE search. Additionally, references cited in published articles were used as data sources.

STUDY SELECTION

Studies describing the epidemiology of Hib disease and the efficacy and/or immunogenicity of the Hib vaccines are reviewed.

DATA SYNTHESIS

Serious invasive disease secondary to Hib infection causes significant morbidity and mortality in children between the ages of three months and five years. The original Hib vaccine was found to be ineffective in stimulating an adequate immune response in children younger than two years of age. The new Hib conjugate vaccines provide superior efficacy and immunogenicity compared with the original unconjugated vaccine. They stimulate an immune response that is distinctly different from that elicited by the original vaccine. Two vaccine products are currently licensed for use in children as young as two months of age, thus conferring immunity to those children at highest risk for Hib disease.

CONCLUSIONS

The new Hib conjugate vaccines provide excellent efficacy and, when used as recommended, may significantly reduce the incidence of invasive Hib disease and its sequelae.

Current trends in bacterial respiratory pathogens

The relationship of virulence and antimicrobial susceptibility with morbidity due to bacterial respiratory pathogens is complex and evolving. Ultimately, decreasing the incidence of pneumonia due to bacterial pathogens will be dependent on successful preparation and distribution of effective vaccines. Until effective vaccines are widely available, control of a majority of respiratory infections will depend on promotion of rational therapeutic strategies. Though limited to a few specific serotypes and strains, changes in virulence of bacterial respiratory pathogens have been noted. Co-infections due to multiple respiratory pathogens may increase morbidity; however, the epidemiology of co-infections is not clear. Relationships between respiratory viruses and bacteria may exist that increase virulence of both agents, but information regarding these relationships awaits further investigation. Resistance of respiratory pathogens to the more commonly used antimicrobials, such as penicillin, erythromycin, chloramphenicol, and cotrimoxazole, is being documented globally with increasing frequency. The evolution of antimicrobic resistance, especially among strains of Streptococcus pneumoniae, the most common and deadly agent of lower respiratory tract infections, provides impetus to develop and promote effective pneumococcal vaccines and to search for new and effective antimicrobials.