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Conjugate Haemophilus influenzae type b vaccines for sickle cell disease
Slimane Allali1, Martin Chalumeau, Odile Launay
1Department of General Pediatrics, Necker Hospital for Sick Children, 149 rue de Sevres, Paris, France, 75015.
Insights
Haemophilus influenzae type b (Hib) conjugate vaccines likely reduce mortality in children with sickle cell disease, though direct trial evidence is lacking. Further research is needed for optimal Hib vaccination schedules in this population.
Area of Science:
- Medical Science
- Immunology
- Hematology
Background:
- Sickle cell disease (SCD) significantly increases susceptibility to invasive Haemophilus influenzae type b (Hib) infections.
- Hib infections historically caused high mortality in young children with SCD before widespread conjugate vaccination.
- Low Hib vaccination coverage in African countries contributes to continued high rates of Hib-related bacteraemia in children with SCD.
Purpose of the Study:
- To determine if Haemophilus influenzae type b (Hib) conjugate vaccines reduce mortality and morbidity in children and adults with sickle cell disease.
- To assess the immunogenicity and safety of Hib conjugate vaccines in individuals with SCD.
- To explore variations in vaccine effectiveness based on vaccine type, administration, dosage, and age.
Main Methods:
- Systematic search of the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register.
- Inclusion criteria: Randomized and quasi-randomized controlled trials comparing Hib conjugate vaccines to placebo or no treatment in individuals with SCD.
- Searches included electronic databases, journal handsearching, conference abstracts, and contact with pharmaceutical companies for unpublished trials.
Main Results:
- No randomized controlled trials (RCTs) were identified that specifically evaluated Haemophilus influenzae type b conjugate vaccines in people with sickle cell disease.
- There is a significant absence of direct evidence from RCTs on the efficacy of Hib conjugate vaccines in the SCD population.
Conclusions:
- A notable decrease in invasive Hib infections in individuals with SCD in high-income countries post-vaccination suggests vaccine benefit.
- Hib conjugate vaccination is strongly expected to improve survival for children with SCD, particularly in regions with low vaccine uptake like Africa.
- Further research is required to establish optimal Hib vaccination schedules for both children and adults with sickle cell disease.
Background:
People affected with sickle cell disease are at high risk of infection from Haemophilus influenzae type b. Before the implementation of Haemophilus influenzae type b conjugate vaccination in high-income countries, this was responsible for a high mortality rate in children under five years of age. In African countries, where coverage of this vaccination is still extremely low, Haemophilus influenzae type b remains one of the most common cause of bacteraemias in children with sickle cell disease. The increased uptake of this conjugate vaccination may substantially improve the survival of children with sickle cell disease.
Objectives:
The primary objective was to determine whether Haemophilus influenzae type b conjugate vaccines reduce mortality and morbidity in children and adults with sickle cell disease.The secondary objectives were to assess the following in children and adults with sickle cell disease: the immunogenicity of Haemophilus influenzae type b conjugate vaccines; the safety of these vaccines; and any variation in effect according to type of vaccine, mode of administration (separately or in combination with other vaccines), number of doses, and age at first dose.
Search Methods:
We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also contacted relevant pharmaceutical companies to identify unpublished trials.Date of last search: 23 November 2015.
Selection Criteria:
All randomised and quasi-randomised controlled trials comparing Haemophilus influenzae type b conjugate vaccines with placebo or no treatment, or comparing different types of Haemophilus influenzae type b conjugate vaccines in people with sickle cell disease.
Data Collection And Analysis:
No trials of Haemophilus influenzae type b conjugate vaccines in people with sickle cell disease were found.
Main Results:
There is an absence of evidence from randomised controlled trials relating to the subject of this review.
Authors' Conclusions:
There has been a dramatic decrease in the incidence of invasive Haemophilus influenzae type b infections observed in the post-vaccination era in people with sickle cell disease living in high-income countries. Therefore, despite the absence of evidence from randomised controlled trials, it is expected that Haemophilus influenzae type b conjugate vaccines may be useful in children affected with sickle cell disease, especially in African countries where there is a high prevalence of the disease. The implementation of childhood immunisation schedules, including universal Haemophilus influenzae type b conjugate vaccination, may substantially improve the survival of children with sickle cell disease living in low-income countries. We currently lack data to evaluate the potential effect of Haemophilus influenzae type b vaccination among unvaccinated adults with sickle cell disease. Further research should assess the optimal Hib immunisation schedule in children and adults with sickle cell disease.
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