Conjugate Haemophilus influenzae type b vaccines for sickle cell disease

Invasive Haemophilus influenzae Infections after 3 Decades of Hib Protein Conjugate Vaccine Use

Haemophilus influenzae serotype b (Hib) was previously the most common cause of bacterial meningitis and an important etiologic agent of pneumonia in children aged <5 years. Its major virulence factor is the polyribosyl ribitol phosphate (PRP) polysaccharide capsule. In the 1980s, PRP-protein conjugate Hib vaccines were developed and are now included in almost all national immunization programs, achieving a sustained decline in invasive Hib infections. However, invasive Hib disease has not yet been eliminated in countries with low vaccine coverage, and sporadic outbreaks of Hib infection still occur occasionally in countries with high vaccine coverage. Over the past 2 decades, other capsulated serotypes have been recognized increasingly as causing invasive infections. H. influenzae serotype a (Hia) is now a major cause of invasive infection in Indigenous communities of North America, prompting a possible requirement for an Hia conjugate vaccine. H. influenzae serotypes e and f are now more common than serotype b in Europe. Significant year-to-year increases in nontypeable H. influenzae invasive infections have occurred in many regions of the world. Invasive H. influenzae infections are now seen predominantly in patients at the extremes of life and those with underlying comorbidities. This review provides a comprehensive and critical overview of the current global epidemiology of invasive H. influenzae infections in different geographic regions of the world. It discusses those now at risk of invasive Hib disease, describes the emergence of other severe invasive H. influenzae infections, and emphasizes the importance of long-term, comprehensive, clinical and microbiologic surveillance to monitor a vaccine's impact.

Conjugate Haemophilus influenzae type b vaccines for sickle cell disease

BACKGROUND

People affected with sickle cell disease (SCD) are at high risk of infection from Haemophilus influenzae type b (Hib). 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, Hib remains one of the most common causes of bacteraemias in children with SCD. The increased uptake of this conjugate vaccination may substantially improve the survival of children with SCD. This is an update of a previously published Cochrane Review.

OBJECTIVES

The primary objective was to determine whether Hib conjugate vaccines reduce mortality and morbidity in children and adults with SCD.The secondary objectives were to assess the following in children and adults with SCD: the immunogenicity of Hib 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 searched trial registries (04 July 2018) and contacted relevant pharmaceutical companies to identify unpublished trials.Date of last search of the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinoapthies Trials Register: 18 December 2017.

SELECTION CRITERIA

All randomised controlled trials (RCTs) and quasi-RCTs comparing Hib conjugate vaccines with placebo or no treatment, or comparing different types of Hib conjugate vaccines in people with SCD.

DATA COLLECTION AND ANALYSIS

No trials of Hib conjugate vaccines in people with SCD were found.

MAIN RESULTS

There is an absence of evidence from RCTs relating to the subject of this review.

AUTHORS' CONCLUSIONS

There has been a dramatic decrease in the incidence of invasive Hib infections observed in the post-vaccination era in people with SCD living in high-income countries. Therefore, despite the absence of evidence from RCTs, it is expected that Hib conjugate vaccines may be useful in children affected with SCD, especially in African countries where there is a high prevalence of the disease. The implementation of childhood immunisation schedules, including universal Hib conjugate vaccination, may substantially improve the survival of children with SCD living in low-income countries. We currently lack data to evaluate the potential effect of Hib vaccination among unvaccinated adults with SCD. Further research should assess the optimal Hib immunisation schedule in children and adults with SCD.