Clinical manifestations and outcome of Haemophilus influenzae type b disease

An invasive Haemophilus influenzae serotype b infection in an Anglo-Saxon plague victim

BACKGROUND

The human pathogen Haemophilus influenzae was the main cause of bacterial meningitis in children and a major cause of worldwide infant mortality before the introduction of a vaccine in the 1980s. Although the occurrence of serotype b (Hib), the most virulent type of H. influenzae, has since decreased, reports of infections with other serotypes and non-typeable strains are on the rise. While non-typeable strains have been studied in-depth, very little is known of the pathogen's evolutionary history, and no genomes dating prior to 1940 were available.

RESULTS

We describe a Hib genome isolated from a 6-year-old Anglo-Saxon plague victim, from approximately 540 to 550 CE, Edix Hill, England, showing signs of invasive infection on its skeleton. We find that the genome clusters in phylogenetic division II with Hib strain NCTC8468, which also caused invasive disease. While the virulence profile of our genome was distinct, its genomic similarity to NCTC8468 points to mostly clonal evolution of the clade since the 6th century. We also reconstruct a partial Yersinia pestis genome, which is likely identical to a published first plague pandemic genome of Edix Hill.

CONCLUSIONS

Our study presents the earliest genomic evidence for H. influenzae, points to the potential presence of larger genomic diversity in the phylogenetic division II serotype b clade in the past, and allows the first insights into the evolutionary history of this major human pathogen. The identification of both plague and Hib opens questions on the effect of plague in immunocompromised individuals already affected by infectious diseases.

Cost-effectiveness of Haemophilus influenzae type b conjugate vaccine in low- and middle-income countries: regional analysis and assessment of major determinants

OBJECTIVES

To estimate the cost-effectiveness of Haemophilus influenzae type b (Hib) conjugate vaccine in low- and middle-income countries and identify the model variables, which are most important for the result.

STUDY DESIGN

A static decision tree model was developed to predict incremental costs and health impacts. Estimates were generated for 4 country groups: countries eligible for funding by the GAVI Alliance in Africa and Asia, lower middle-income countries, and upper middle-income countries. Values, including disease incidence, case fatality rates, and treatment costs, were based on international country estimates and the scientific literature.

RESULTS

From the societal perspective, it is estimated that the probability of Hib conjugate vaccine cost saving is 34%-53% in Global Alliance for Vaccines and Immunization eligible African and Asian countries, respectively. In middle-income countries, costs per discounted disability adjusted life year averted are between US$37 and US$733. Variation in vaccine prices and risks of meningitis sequelae and mortality explain most of the difference in results. For all country groups, disease incidence cause the largest part of the uncertainty in the result.

CONCLUSIONS

Hib conjugate vaccine is cost saving or highly cost-effective in low- and middle-income settings. This conclusion is especially influenced by the recent decline in Hib conjugate vaccine prices and new data revealing the high costs of lost productivity associated with meningitis sequelae.

Global and regional risk of disabling sequelae from bacterial meningitis: a systematic review and meta-analysis

Few data sources are available to assess the global and regional risk of sequelae from bacterial meningitis. We aimed to estimate the risks of major and minor sequelae caused by bacterial meningitis, estimate the distribution of the different types of sequelae, and compare risk by region and income. We systematically reviewed published papers from 1980 to 2008. Standard global burden of disease categories (cognitive deficit, bilateral hearing loss, motor deficit, seizures, visual impairment, hydrocephalus) were labelled as major sequelae. Less severe, minor sequelae (behavioural problems, learning difficulties, unilateral hearing loss, hypotonia, diplopia), and multiple impairments were also included. 132 papers were selected for inclusion. The median (IQR) risk of at least one major or minor sequela after hospital discharge was 19.9% (12.3-35.3%). The risk of at least one major sequela was 12.8% (7.2-21.1%) and of at least one minor sequela was 8.6% (4.4-15.3%). The median (IQR) risk of at least one major sequela was 24.7% (16.2-35.3%) in pneumococcal meningitis; 9.5% (7.1-15.3%) in Haemophilus influenzae type b (Hib), and 7.2% (4.3-11.2%) in meningococcal meningitis. The most common major sequela was hearing loss (33.9%), and 19.7% had multiple impairments. In the random-effects meta-analysis, all-cause risk of a major sequela was twice as high in the African (pooled risk estimate 25.1% [95% CI 18.9-32.0%]) and southeast Asian regions (21.6% [95% CI 13.1-31.5%]) as in the European region (9.4% [95% CI 7.0-12.3%]; overall I(2)=89.5%, p<0.0001). Risks of long-term disabling sequelae were highest in low-income countries, where the burden of bacterial meningitis is greatest. Most reported sequelae could have been averted by vaccination with Hib, pneumococcal, and meningococcal vaccines.

The burden of pneumonia in children: an Australian perspective

The burden of pneumonia in Australian children is significant with an incidence of 5-8 per 1000 person-years. Pneumonia is a major cause of hospital admission in children less than 5 years of age. Indigenous children are at particular risk with a 10-20-fold higher risk of hospitalisation compared to non-Indigenous children. They also have longer admissions and are more likely to have multiple admissions with pneumonia. There are limited data on pathogen-specific causes of pneumonia, however Streptococcus pneumonia is the most common bacterial cause in children under 5 years of age and respiratory syncytial virus (RSV) and influenza are the predominant viral causes in young children. Pneumonia due to Haemophilus influenza type b (Hib) has been virtually eliminated by the introduction of universal Hib immunisation. Further studies are needed to accurately define the epidemiology of pneumonia due to specific pathogens to help target treatment and immunisation strategies.

Epidemiology of bacterial meningitis among children in Brazil, 1997-1998

OBJECTIVE

To document the incidence and the descriptive epidemiology of bacterial meningitis among individuals under age 20 in a geographically defined region in Brazil during the two-year period immediately preceding the introduction of Haemophilus influenzae type b (Hib) vaccines into the national immunization program of Brazil.

METHODS

Population-based epidemiological study of all cases of bacterial meningitis reported among residents of Campinas, Brazil, under age 20 (n=316,570) during the period of 1997-98, using comprehensive surveillance records compiled by the Campinas Health Department from cases reported among hospital inpatients, outpatients, emergency room visits, death certificates, and autopsy reports.

RESULTS

The incidence of bacterial meningitis (n=274) was 334.9, 115 and 43.5 cases/10(5) person-years (pys) for residents of Campinas under age 1, 5 and 20, respectively. All cases were hospitalized, with an average length of stay of 12 days. Documented prior antibiotic use was 4.0%. The case-fatality rate of bacterial meningitis in individuals under age 20 was 9% (24/274) with 75% of deaths occurring in children under the age of five. The incidence of Hib meningitis (n=26) was 62.8 and 17 cases/10(5) pys in children age <1 and <5, respectively.

CONCLUSIONS

The incidence of Hib meningitis in children under the age of 5 in Campinas during 1997-98 was similar to that reported in the US, Western Europe, and Israel prior to widespread Hib vaccine use in those regions. This study provides a baseline for later studies to evaluate changes in the etiology and incidence of bacterial meningitis in children after introduction of routine Hib vaccination in Brazil.

Cost-benefit analysis of a Haemophilus influenzae type b meningitis prevention programme in The Philippines

BACKGROUND

Haemophilus influenzae type b (Hib) meningitis is associated with high mortality and serious sequelae in children under 5 years of age. Vaccines which can prevent this infection are available.

OBJECTIVE

To evaluate the costs and benefits of a 3-dose immunisation schedule in Manila, Philippines.

PERSPECTIVE

Government and societal perspectives.

DESIGN AND PARTICIPANTS

A cost-benefit analysis based on a birth cohort of 100,000 children. The state of health of the cohort with and without a Hib immunisation programme was modelled over a 5-year period. A survey of medical records of patients with Hib in Manila provided data on the extent and cost of sequelae following infection.

INTERVENTION

A 3-dose Hib vaccination programme given at ages 2, 3 and 4 months.

RESULTS

The model predicted that vaccinating children against Hib meningitis would prevent 553 cases per year in a birth cohort of 100,000, at a cost of 56,200 Philippine pesos (PHP) [$US1,605; 1998 exchange rate] per case (base case assumptions of 90% vaccine efficacy rate, 95 per 100,000 Hib incidence rate, 85% vaccination coverage). Results from the cost-benefit analyses indicated that the saving to the government would be around PHP39 million ($US1.11 million), and the saving to society would be PHP255 million ($US7.28 million).

CONCLUSION

There would be a positive economic benefit for the Philippine government and for the Filipino society if a Hib vaccination programme was introduced in Manila.

The introduction of routine Haemophilus influenzae type b conjugate vaccine in Chile: a framework for evaluating new vaccines in newly industrializing countries

OBJECTIVE

To determine the burden of Haemophilus influenzae type b (Hib) disease, the safety and immunogenicity of Hib conjugate vaccine, the practicality of combining Hib conjugate and diphtheria-tetanus-pertussis vaccines and the effectiveness of routine vaccination.

STUDY DESIGNS

A series of studies were carried out involving infants and children in Santiago, Chile. The study designs included retrospective surveillance, cost-benefit analysis, randomized placebo-controlled trials of safety and immunogenicity and a Phase IV postlicensure evaluation of vaccine effectiveness.

RESULTS

The studies included in this stepwise process showed that Hib invasive disease was a significant public health problem with a substantial economic burden; that combining Hib conjugate and diphtheria-tetanus-pertussis vaccines was practical, safe and elicited a strong immunologic response; and that the combined formulation afforded a high level of protection against invasive Hib disease (90% effectiveness).

CONCLUSIONS

In July, 1996, Chile became only the third newly industrializing country to introduce routine Hib conjugate vaccination. New vaccines, such as Hib conjugates, will be more expensive than existing ones. The stepwise process used in Chile may serve as an example for the evaluation of new vaccines in nonindustrialized countries.

Sporadic invasion of cultured epithelial cells by Haemophilus influenzae type b

While working with an in vitro invasion assay, we observed that Haemophilus influenzae type b occasionally exhibits highly invasive behavior. The phenomenon is not inhibited by colchicine or cytochalasin but is dependent on the presence of supplemental CO2. We propose that sporadic invasiveness may correlate with the unknown events that precede Haemophilus influenzae type b bacteremia.

Differing antibody responses to Haemophilus influenzae type b after meningitis or epiglottitis

Two common forms of invasive disease due to Haemophilus influenzae type b (Hib) are epiglottitis and meningitis. It is not known why some children develop epiglottitis and others meningitis. To examine the hypothesis that epiglottitis occurs in children who may have been previously exposed to Hib, and who would therefore exhibit a more vigorous antibody response in convalescence, we measured levels of antibody to Hib capsule in 92 children. Geometric mean convalescent-phase IgG, IgA, IgM and total antibody levels were significantly higher in 45 children with epiglottitis than in 47 with meningitis, even after adjustment for age differences (mean total antibody, 95% confidence intervals: meningitis 0.38, 0.34-0.43; epiglottitis: 2.25, 2.0-2.54 micrograms/ml). However, contrary to previous reports, a poor antibody response was only observed in a minority of children with meningitis; the antibody response of the majority was indistinguishable from that observed in children with epiglottitis.