The burden and impact of severe and long-term sequelae of meningococcal disease

Cost-effectiveness analysis of vaccination strategies against meningococcal disease for children under nine years of age in China

Meningococcal vaccination strategies in China are intricate, including multiple vaccines targeting different serogroups. The current National Immunization Program (NIP) includes two polysaccharide vaccines for serogroups A and C (MPV-A and MPV-AC), covering limited serogroups and requiring adaptation. This study aims to evaluate the cost-effectiveness of replacing the current strategy with alternative strategies utilizing non-NIP vaccines to inform policy decisions. From a societal perspective, a decision tree-Markov model was constructed to simulate the economic and health consequences of meningococcal disease in a 2019 birth cohort with four vaccination strategies. Epidemiology, vaccine efficacy, cost, and other parameters were derived from previous studies. We conducted sensitivity analyses to assess the robustness of the findings and explored prices for non-NIP vaccines that enable cost-effective strategies. Compared to the current strategy, alternative strategies using quadrivalent polysaccharide vaccine (MPV-4), bivalent conjugate vaccine (MCV-AC), and quadrivalent conjugate vaccine (MCV-4) could avoid 91, 286, and 455 more meningococcal cases. The ICERs were estimated at approximately $250 thousand/QALY, $450 thousand/QALY, and $1.5 million/QALY, all exceeding the threshold of three times GDP per capita. The alternative strategies were not cost-effective. However, if vaccine prices were reduced to $3.9 for MPV-4, $9.9 for MCV-AC, and $12 for MCV-4, the corresponding strategy would be cost-effective. The current meningococcal vaccination strategy in China could effectively prevent the disease at a low cost, but with limited serogroup coverage. Strategies using MPV-4, MCV-AC, or MCV-4 could increase health benefits at a substantial cost, and might become cost-effective if vaccine prices decrease.

Monophosphoryl Lipid A-based Adjuvant to Promote the Immunogenicity of Multivalent Meningococcal Polysaccharide Conjugate Vaccines

Activation of the adaptive immune system requires the engagement of costimulatory pathways in addition to B and T cell Ag receptor signaling, and adjuvants play a central role in this process. Many Gram-negative bacterial polysaccharide vaccines, including the tetravalent meningococcal conjugate vaccines (MCV4) and typhoid Vi polysaccharide vaccines, do not incorporate adjuvants. The immunogenicity of typhoid vaccines is due to the presence of associated TLR4 ligands in these vaccines. Because the immunogenicity of MCV4 is poor and requires boosters, I hypothesized that TLR4 ligands are absent in MCV4 and that incorporation of a TLR4 ligand-based adjuvant would improve their immunogenicity. Consistent with this hypothesis, two Food and Drug Administration-approved MCV4 vaccines, MENVEO and MenQuadfi, lack TLR4 ligands. Admixing monophosphoryl lipid A, a TLR4 ligand-based adjuvant formulation named "Turbo" with MCV4 induced significantly improved IgM and IgG responses to all four meningococcal serogroup polysaccharides in adult and aged mice after a single immunization. Furthermore, in infant mice, a single booster was sufficient to promote a robust IgG response and 100% seroconversion when MCV4 was adjuvanted with Turbo. Turbo upregulated the expression of the costimulatory molecules CD40 and CD86 on B cells, and Turbo-driven adjuvanticity is lost in mice deficient in CD40 and CD86. These data suggest that Turbo induces the required costimulatory molecules for its adjuvant activity and that incorporation of Turbo could make bacterial polysaccharide vaccines more immunogenic, minimize booster requirements, and be cost-effective, particularly for those individuals in low- and middle-income and disease-endemic countries.

Clinical Predictors and Biomarkers in Children With Sepsis and Bacterial Meningitis

OBJECTIVES

Sepsis and meningitis in children may present with different clinical features and a wide range of values of inflammatory markers. The aim of this study was to identify the prognostic value of clinical features and biomarkers in children with sepsis and bacterial meningitis in the emergency department (ED).

METHODS

We carried out a single-center, retrospective, observational study on 194 children aged 0 to 14 years with sepsis and bacterial meningitis admitted to the pediatric ED of a tertiary children's hospital through 12 years.

RESULTS

Among epidemiological and early clinical features, age older than 12 months, capillary refill time greater than 3 seconds, and oxygen blood saturation lower than 90% were significantly associated with unfavorable outcomes, along with neurological signs ( P < 0.05). Among laboratory tests, only procalcitonin was an accurate and early prognostic biomarker for sepsis and bacterial meningitis in the ED, both on admission and after 24 hours. Procalcitonin cut-off value on admission for short-term complications was 19.6 ng/mL, whereas the cut-off values for long-term sequelae were 19.6 ng/mL on admission and 41.9 ng/mL after 24 hours, respectively. The cut-off values for mortality were 18.9 ng/mL on admission and 62.4 ng/mL at 24 hours.

CONCLUSIONS

Procalcitonin, along with clinical evaluation, can guide the identification of children at higher risk of morbidity and mortality, allowing the most appropriate monitoring and treatment.

Invasive meningococcal disease in Malaysia, Philippines, Thailand, and Vietnam: An Asia-Pacific expert group perspective on current epidemiology and vaccination policies

Invasive meningococcal disease (IMD) imposes a significant burden on the global community due to its high case fatality rate (4-20%) and the risk of long-term sequelae for one in five survivors. An expert group meeting was held to discuss the epidemiology of IMD and immunization policies in Malaysia, Philippines, Thailand, and Vietnam. Most of these countries do not include meningococcal immunization in their routine vaccination programs, except for high-risk groups such as immunocompromised people and pilgrims. It is difficult to estimate the epidemiology of IMD in the highly diverse Asia-Pacific region, but available evidence indicate serogroup B is increasingly dominant. Disease surveillance systems differ by country. IMD is not a notifiable disease in some of them. Without an adequate surveillance system in the region, the risk and the burden of IMD might well be underestimated. With the availability of new combined meningococcal vaccines and the World Health Organization roadmap to defeat bacterial meningitis by 2030, a better understanding of the epidemiology of IMD in the Asia-Pacific region is needed.

Complications Associated with Foodborne Listeriosis: A Scoping Review

Listeria monocytogenes is a relatively rare but highly pathogenic bacterium that can cause foodborne infections. In the United States there are ∼1600 cases per year, 94% of which result in hospitalizations and 20% in deaths. Per-case burden is high because the disease also causes serious complications, including sepsis, encephalitis, meningitis, miscarriage, and stillbirth. The disease burden of L. monocytogenes is underestimated because some of these acute complications can also result in long-term outcomes. In this article, we conducted a scoping review of L. monocytogenes complications and longer term outcomes from articles published between 2000 and 2018. Search terms were developed for four major databases (PubMed, Scopus, Web of Science, and Embase) as well as gray literature and hand searches of review articles. We follow standard scoping review methodology and assessment. Out of 10,618 unique articles originally identified, 115 articles were included, representing 49 unique outcomes. The majority of studies were cohort designs (n = 67) and conducted in the United States or Europe (n = 98). Four major outcome groupings were death, neurological disorders, sepsis, and congenital infection. This study identifies substantial research on the common acute complications of L. monocytogenes and few long-term consequences of L. monocytogenes. We identify the need for additional studies to determine the longer term impacts of these acute complications.

Demographic Features of Invasive Meningococcal Disease in Taiwan, 1993 to 2020, and Genetic Characteristics of Neisseria meningitidis Isolates, 2003 to 2020

We present the demographic features of invasive meningococcal disease (IMD) in Taiwan between 1993 and 2020 and the genetic characteristics of Neisseria meningitidis isolates recovered from 2003 to 2020. IMD was rare in Taiwan between 1993 and 2020, with an annual incidence ranging from 0.009 to 0.204 per 100,000 people. The case fatality rate (CFR) declined from 18.1% for patients in 1993 to 2002 to 9.8% in 2003 to 2020. Infants less than 12 months were most susceptible to the disease. N. meningitidis serogroup B (NmB) was most predominant, responsible for 81.2% (134/165) of the IMD cases in 2003 to 2020. The majority of the isolates recovered from 2003 to 2020 belonged to 4 worldwide-spread hyperinvasive clonal complexes (cc), cc4821 (30.3%), cc32 (19.4%), cc41/44 (12.7%), cc23 (7.3%), and also a newly assigned clonal complex, cc3439 (10.3%). Core genome multilocus sequence typing (cgMLST) profile comparisons revealed that the cc4821 isolates with a T-to-I substitution at position 91 in gyrA were closely related to those originating from China. Of the 165 isolates, 20.0% and 53.3% were predicted to be covered by the Bexsero and Trumenba vaccines, respectively, whereas, 77.0% and 46.7% remained indeterminate. In conclusion, N. meningitidis isolates recovered in Taiwan between 2003 and 2020 were mostly highly diverse. Most IMD cases appeared sporadically and were caused by localized strains, although some patients were infected by recently introduced strains. cgMLST is a powerful tool for the rapid comparison of genetic relatedness among a large number of isolates. cgMLST profiling, based on 1,241 core genes, and strain tracking can be performed on the website of cgMLST@Taiwan (http://rdvd.cdc.gov.tw/cgMLST/). IMPORTANCE N. meningitidis can cause life-threatening invasive meningococcal disease (IMD), including meningitis and sepsis, resulting in a high CFR and long-term sequelae in survivors. Here, we report the demographic features of IMD in Taiwan over a 28-year period (1993 to 2020) and the genetic characteristics of N. meningitidis isolates recovered from patients with IMD over an 18-year period (2003 to 2020). We conducted a whole-genome sequence analysis to characterize the genetic features of the isolates and developed a cgMLST scheme for epidemiological investigation and strain tracking. The findings can be beneficial in understanding the epidemiology of IMD in Taiwan, the genetic characteristics of the bacterial strains, and the distribution of vaccine antigens for vaccine development and implementation.

Care pathways in invasive meningococcal disease: a retrospective analysis of the French national public health insurance database

Invasive meningococcal disease (IMD) carries a high burden in terms of mortality, long-term complications, and cost, which can be significantly reduced by vaccination. The objectives of this case–control study were to document the care pathways of patients with IMD before, during, and after hospitalization and to assess in-hospital complications and long-term sequelae. Cases consisted of all people hospitalized for IMD in France between 2012 and 2017. Controls were matched by age, gender, and district of residence. Data were extracted from the French national public health insurance database on demographics, hospitalizations, mortality and potential sequelae of IMD. Overall, 3,532 cases and 10,590 controls were assessed and followed up for 2.8 years (median). During hospitalization, 1,577 cases (44.6%) stayed in an intensive care unit, 1,238 (35.1%) required mechanical ventilation, and 43 (1.2%) underwent amputation; 293 cases (8.3%) died in hospital and a further 163 (4.6%) died following discharge; 823 cases (25.4% of survivors) presented ≥1 sequela and 298 (9.2%) presented multiple sequelae. The most frequently documented sequelae were epilepsy (N = 205; 5.8%), anxiety (N = 196; 5.5%), and severe neurological disorders (N = 193; 5.5%). All individual sequelae were significantly more frequent (p < .0001) in cases than controls. Hearing/visual impairment and communication problems were conditions that presented the highest risk for cases compared to controls (risk ratios >20 in all cases). In conclusion, this study highlights the importance of providing optimal medical care for patients with IMD, of minimizing the delay before hospitalization, and of effective prevention through comprehensive vaccination programs.

Benefits of providing optimal medical care for IMD patients.

Importance of minimising the delay before hospitalization.

IMD remains challenging to diagnose, and vaccination is the most efficient way to prevent the disease and its complications.

Vaccine impact and effectiveness of meningococcal serogroup ACWY conjugate vaccine implementation in the Netherlands: a nationwide surveillance study

Background

In response to the recent serogroup W invasive meningococcal disease (IMD-W) epidemic in the Netherlands, meningococcal serogroup C (MenC) conjugate vaccination for children aged 14 months was replaced with a MenACWY conjugate vaccination, and a mass campaign targeting individuals aged 14–18 years was executed. We investigated the impact of MenACWY vaccination implementation in 2018–2020 on incidence rates and estimated vaccine effectiveness (VE).

Methods

We extracted IMD cases diagnosed between July 2014 and December 2020 from the national surveillance system. We calculated age group–specific incidence rate ratios by comparing incidence rates before (July 2017–March 2018) and after (July 2019–March 2020) MenACWY vaccination implementation. We estimated VE in vaccine-eligible cases using the screening method.

Results

Overall, the IMD-W incidence rate declined by 61% (95% confidence interval [CI], 40 to 74). It declined by 82% (95% CI, 18 to 96) in the vaccine-eligible age group (individuals aged 15–36 months and 14–18 years) and by 57% (95% CI, 34 to 72) in vaccine-noneligible age groups. VE was 92% (95% CI, –20 to 99.5) in vaccine-eligible toddlers (aged 15–36 months). No IMD-W cases were reported in vaccine-eligible teenagers after the campaign.

Conclusions

The MenACWY vaccination program was effective in preventing IMD-W in the target population. The IMD-W incidence reduction in vaccine-noneligible age groups may be caused by indirect effects of the vaccination program. However, disentangling natural fluctuation from vaccine effect was not possible. Our findings encourage the use of toddler and teenager MenACWY vaccination in national immunization programs.

Healthcare Resource Consumption and Cost of Invasive Meningococcal Disease in France: A Study of the National Health Insurance Database

Introduction

Invasive meningococcal disease (IMD) is an uncommon but serious infectious disease. Its economic burden is known to be high but is poorly characterised. The objective of this study was to determine costs, as captured in the healthcare claims database, incurred by all patients hospitalised for IMD in France over a 6-year period.

Methods

This case–control study was performed using the French national public health insurance database (SNDS). Cases comprised all individuals hospitalised with acute IMD in France between 2012 and 2017 inclusive. For each case, three controls were identified, matched for age, gender and region of residence. All healthcare resource consumption by cases and controls during the follow-up period was documented. Costs were analysed for the index hospitalisation in cases, 1 year following the index date and then for 5 years following the index date. Costs were assigned from national tariffs. The analysis was performed from a societal perspective. IMD sequelae were identified from hospital discharge summaries.

Results

A total of 3532 cases and 10,590 controls were evaluated. The mean per capita cost of the index IMD hospitalisation was €11,256, and increased with age and with the presence of sequelae. In the year following the index date, mean per capita direct medical costs were €6564 in cases and €2890 in controls. Annual costs were €4254 in cases without sequelae, €10,799 in cases with one sequela and €20,096 in cases with more than one sequela. In the fifth year of follow-up, mean per capita costs were €2646 in cases and €1478 in controls. The excess cost in cases was principally due to the management of sequelae. Amputation, skin scarring and mental retardation generated per capita costs in excess of €20,000 in the first year and in excess of €10,000 for subsequent years.

Conclusion

The economic burden of IMD in France is high and, over the long-term, is driven by sequelae management.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00468-w.

Risk factors for invasive meningococcal disease: a retrospective analysis of the French national public health insurance database

Vaccination of at-risk populations against Neisseria meningitidis is an important strategy to prevent invasive meningococcal disease (IMD). The objective of this study was to characterize preexisting risk factors in patients with IMD and to compare their relative importance. This case-control analysis was performed in the French national public health insurance database (SNDS). Cases consisted of all people hospitalized for IMD in France over a six-year period (2012–2017). Controls were matched by age, gender, and district of residence. Medical risk factors were identified from ICD-10 codes in the SNDS. Socioeconomic risk factors studied were low household income and social deprivation of the municipality of residence. Associations of these risk factors with hospitalization for IMD were quantified as odds ratios (ORs) between cases and controls with their 95% confidence intervals (95%CI). The medical risk factors showing the most robust associations were congenital immunodeficiency (OR: 39.1 [95%CI: 5.1–299], acquired immunodeficiency (10.3 [4.5–24.0]) and asplenia/hyposplenia (6.7 [3.7–14.7]). In addition, certain chronic medical conditions, such as autoimmune disorders (5.4 [2.5–11.8]), hemophilia (4.7 [1.8–12.2]) and severe chronic respiratory disorders (4.3 [3.1–6.2]) were also strongly associated, as was low household income (1.68 [1.49–1.80]). In conclusion, this study has documented potential risk factors associated with hospitalization for IMD in a large and comprehensive sample of individuals with IMD in France. Several of the risk factors identified may help identify groups who could benefit from targeted prevention measures (such as vaccination) in order to reduce the burden of IMD.

Why the Anti-Meningococcal B Vaccination during Adolescence Should Be Implemented in Italy: An Overview of Available Evidence

Although meningococcal disease has a low incidence in Italy, it is a public health concern owing to its high lethality rate and high frequency of transitory and/or permanent sequelae among survivors. The highest incidence rates are recorded in infants, children and adolescents, and most of the cases are due to Neisseria meningitidis B. In Italy, anti-meningococcal B (anti-MenB) vaccination is free for infants but, despite the considerable disease burden in adolescents, no national recommendation to vaccinate in this age-group is currently available. The aim of this study was to assess the main available scientific evidence to support the Italian health authorities in implementing a program of free anti-MenB vaccination for adolescents. We conducted an overview of the scientific literature on epidemiology, disease burden, immunogenicity and safety of available vaccines, and economic evaluations of vaccination strategies. Each case of invasive meningococcal disease generates a considerable health burden (lethality rate: 9%; up to 60% of patients experience at least one sequela) in terms of impaired quality of life for survivors and high direct and indirect costs (the mean overall cost of acute phase for a single case amounts to about EUR 13,952; the costs for post-acute and the long-term phases may vary widely depending of the type of sequela, reaching an annual cost of about EUR 100,000 in cases of severe neurological damage). Furthermore, vaccination against meningococcus B in adolescence proved cost-effective. The study highlights the need to actively offer the anti-MenB vaccination during adolescence at a national level. This would make it possible to avoid premature deaths and reduce the high costs borne by the National Health Service and by society of supporting survivors who suffer temporary and/or permanent sequelae.

High genomic-based predicted strain coverage among invasive meningococcal isolates when combining Bexsero and Trumenba vaccines

Two protein-based vaccines (Bexsero® and Trumenba®) are licensed for invasive meningococcal disease (IMD) caused by Neisseria meningitidis serogroup B (MenB). The aim of this study was to evaluate the possible protection of these vaccines, based on the genomic profiles of IMD isolates. All invasive meningococcal isolates in Sweden during 2014-2018 (n = 242) were analyzed with the vaccine coverage scheme available at the PubMLST database. The overall estimated genomic strain coverage among the Swedish invasive meningococcal isolates was 55% for Bexsero and 57% for Trumenba (p = 0.714). The estimated serogroup-specific coverage for Bexsero respectively Trumenba was: MenB; 67% and 90% (p < 0.05), MenW; 93% and 4% (p < 0.05), MenC; 87% and 30% (p < 0.05) and MenY; 1% and 96% (p < 0.05). With the combination of the two vaccines, the potential genomic-based strain coverage was 95%, indicating a possible additive effect of combining Bexsero and Trumenba, which, however, needs to be confirmed by analysis of phenotypic antigen expression.

Clinical Description and Outcomes of Australian Children With Invasive Group A Streptococcal Disease

BACKGROUND

Invasive group A streptococcal disease is a severe infection with a high case fatality rate, estimated to cause more than 150,000 deaths per year worldwide. The clinical presentation of this infection is variable, and early diagnosis can be challenging. There are few data on its short- and longer-term outcomes, especially in children. The aim of this study was to assess the clinical presentation, management and short- and longer-term outcomes of invasive group A streptococcal disease in children in Australia.

METHODS

We undertook a prospective surveillance study of children with laboratory-confirmed invasive group A streptococcus disease admitted to 7 sentinel tertiary and quaternary pediatric hospitals in Australia between July 2016 and June 2018. We collected demographic and clinical data and contacted patients 6 months after discharge to assess longer-term outcomes.

RESULTS

We enrolled 181 children, 7 days to 16 years of age. The principal site of invasive infection was blood (126 children, 69.6%), and the most frequent clinical presentation was pneumonia in 46 children (25.4%). Twenty-six children developed streptococcal toxic shock syndrome (14.4%), and 74 had severe disease (40.9%), including 71 admitted to the intensive care unit. Five children died (2.8%). At discharge and 6 months, 29.3% and 15.2% of the children had persisting health problems, respectively.

CONCLUSIONS

Invasive group A streptococcal infection in Australian children is frequently severe and has a high long-term morbidity burden, highlighting the need for strengthened clinical care pathways, epidemiologic surveillance and prevention strategies.

The spread of chloramphenicol-resistant Neisseria meningitidis in Southeast Asia

•

Chloramphenicol resistant strains of Neisseria meningitidis are present in three countries across Southeast Asia.

•

These strains are all closely related to each other and to resistant strains previously observed in Vietnam and France.

•

This lineage has acquired other antimicrobial resistance genes during its spread.

Objectives

Invasive disease caused by Neisseria meningitidis is a significant health concern globally, but our knowledge of the prevailing serogroups, antimicrobial susceptibility patterns, and genetics of N. meningitidis in Southeast Asia is limited. Chloramphenicol resistance in N. meningitidis has rarely been reported, but was first described in isolates from Vietnam in 1998. We aimed to characterise eight chloramphenicol resistant meningococcal isolates collected between 2007 and 2018 from diagnostic microbiology laboratories in Cambodia, Thailand and the Lao People's Democratic Republic (Laos).

Methods

Whole-genome sequencing was used to generate genome sequences from 18 meningococcal isolates including the eight chloramphenicol resistant isolates. We identified antimicrobial resistance genes present in these strains, and examined the phylogenetic relationships between strains.

Results

The eight resistant strains all contain the same chloramphenicol resistance gene first described in 1998, and are closely related to each other. Strains resistant to penicillin, tetracycline, and ciprofloxacin were also observed, including a chloramphenicol-resistant strain which has acquired penicillin and ciprofloxacin resistance.

Conclusions

This study suggests that chloramphenicol-resistant N. meningitidis is more widespread than previously thought, and that the previously-identified resistant lineage is now found in multiple countries in Southeast Asia.

Understanding immunogenicity assessments for meningococcal serogroup B vaccines

Invasive meningococcal disease (IMD) is a potentially devastating infection associated with high mortality and long-term sequelae; however, vaccines are available to protect against the five common disease-causing serogroups (A, B, C, W, and Y). Because traditional field efficacy clinical trials were not feasible due to low IMD incidence that necessitates a very large number of participants, serum bactericidal antibody (SBA) assays using rabbit (rSBA) or human (hSBA) complement were established as in vitro surrogates of meningococcal vaccine efficacy and are now routinely used to support vaccine licensure. Specifically, rSBA assays have been used to evaluate responses to meningococcal capsular polysaccharide-protein conjugate vaccines against serogroups A, C, W, and Y; the accepted correlate of protection for rSBA assays is a titer ≥1:8. Importantly, because the bacterial capsular polysaccharide antigen is conserved across strains, only one test strain that expresses an invariant polysaccharide capsule for each serogroup is required to assess coverage. rSBA assays are unsuitable for subcapsular protein-based serogroup B (MenB) vaccines, and therefore, hSBA assays have been used for licensure; titers ≥1:4 are considered the correlate of protection against IMD for hSBA. In contrast to MenACWY vaccines, because bacterial surface proteins are antigenically variable, MenB vaccines must be tested with hSBA assays using multiple test strains that represent the antigenic diversity of disease-causing isolates. As this complexity regarding SBA assessment methods can make data interpretation difficult, herein we describe the use of hSBA assays to evaluate MenB vaccine efficacy and to support licensure. In addition, we highlight how the two recently approved MenB vaccines differ in their use of hSBA assays in clinical studies to demonstrate broad protection against MenB IMD.

Economic evaluation of meningococcal vaccines: considerations for the future

In 2018, a panel of health economics and meningococcal disease experts convened to review methodologies, frameworks, and decision-making processes for economic evaluations of vaccines, with a focus on evaluation of vaccines targeting invasive meningococcal disease (IMD). The panel discussed vaccine evaluation methods across countries; IMD prevention benefits that are well quantified using current methods, not well quantified, or missing in current cost-effectiveness methodologies; and development of recommendations for future evaluation methods. Consensus was reached on a number of points and further consideration was deemed necessary for some topics. Experts agreed that the unpredictability of IMD complicates an accurate evaluation of meningococcal vaccine benefits and that vaccine cost-effectiveness evaluations should encompass indirect benefits, both for meningococcal vaccines and vaccines in general. In addition, the panel agreed that transparency in the vaccine decision-making process is beneficial and should be implemented when possible. Further discussion is required to ascertain: how enhancing consistency of frameworks for evaluating outcomes of vaccine introduction can be improved; reviews of existing tools used to capture quality of life; how indirect costs are considered within models; and whether and how the weighting of quality-adjusted life-years (QALY), application of QALY adjustment factors, or use of altered cost-effectiveness thresholds should be used in the economic evaluation of vaccines.

Neisseria meningitidis: using genomics to understand diversity, evolution and pathogenesis

Meningococcal disease remains an important cause of morbidity and death worldwide despite the development and increasing implementation of effective vaccines. Elimination of the disease is hampered by the enormous diversity and antigenic variability of the causative agent, Neisseria meningitidis, one of the most variable bacteria in nature. These features are attained mainly through high rates of horizontal gene transfer and alteration of protein expression through phase variation. The recent availability of whole-genome sequencing (WGS) of large-scale collections of N. meningitidis isolates from various origins, databases to facilitate storage and sharing of WGS data and the concomitant development of effective bioinformatics tools have led to a much more thorough understanding of the diversity of the species, its evolution and population structure and how virulent traits may emerge. Implementation of WGS is already contributing to enhanced epidemiological surveillance and is essential to ascertain the impact of vaccination strategies. This Review summarizes the recent advances provided by WGS studies in our understanding of the biology of N. meningitidis and the epidemiology of meningococcal disease.

Lifetime costs of invasive meningococcal disease: A Markov model approach

INTRODUCTION

Invasive meningococcal disease (IMD) is an uncommon but life-threatening infectious disease associated with high sequelae rates in young children and an increased risk of mortality in adolescents and young adults. Funding decisions to reject inclusion of new meningococcal serogroup B vaccines on national immunisation schedules have been criticised by IMD patients, their families, paediatricians and charity organisations. We aim to estimate the lifetime costs of IMD with the best available evidence to inform cost-effectiveness analyses.

METHODS

A Markov model was developed taking healthcare system and societal perspectives. A range of data including age-specific mortality rates, and probabilities of IMD-related sequelae were derived from a systematic review and meta-analysis. All currencies were inflated to year 2017 prices by using consumer price indexes in local countries and converted to US dollars by applying purchasing power parities conversion rates. Expert panels were used to inform the model development process including key structural choices and model validations.

RESULTS

The estimated lifetime societal cost is US$319,896.74 per IMD case including the direct healthcare cost of US$65,035.49. Using a discount rate of 5%, the costs are US$54,278.51 and US$13,968.40 respectively. Chronic renal failure and limb amputation result in the highest direct healthcare costs per patient. Patients aged < 5 years incur the higher healthcare expenditure compared with other age groups. The costing results are sensitive to the discount rate, disease incidence, acute admission costs, and sequelae rates and costs of brain injuries and epilepsy.

CONCLUSIONS

IMD can result in substantial costs to the healthcare system and society. Understanding the costs of care can assist decision-making bodies in evaluating cost-effectiveness of new vaccine programs.

Cost-effectiveness of meningococcal polysaccharide serogroups A, C, W-135 and Y conjugate vaccine in Australian adolescents

OBJECTIVES

The incidence of invasive meningitis disease (IMD) is increasing in Australia. A conjugate vaccine of meningococcal polysaccharide serogroups A, C, W and Y (MenACWY) is currently indicated for infants aged 12 months on the Australian National Immunisation Program. This study sought to determine the cost-effectiveness of a broader MenACWY vaccination program for Australians aged 15 to 19 years.

METHODS

A Markov model was constructed to simulate the incidence and consequences of IMD in Australians aged 0-84 years, with follow up until age 85 years. The model comprised four health states: 'Alive with no previous IMD', 'Alive, post IMD without long-term complications', 'Alive, post IMD with long-term complications' and 'Dead'. Decision analysis compared the clinical consequences and costs of a vaccination program versus no vaccination from the perspective of the Australian health care system. Age-specific incidence of IMD and fatality rates were derived from Australian surveillance data. Vaccine coverage, vaccine efficacy and herd immunity were based on published data. The total cost for MenACWY vaccination was AU$56 per dose. Costs and health outcomes were discounted by 5% per annum (in the base-case analysis).

RESULTS

Compared to no vaccination, a MenACWY vaccination program targeted at Australians aged 15-19 years was expected to prevent 1664 IMD cases in the Australian population aged 0-84 years followed up until age 85 years. The program would lead to 1131 life years (LYs) and 2058 quality adjusted life years (QALYs) gained at a total cost of AU$115 million (all discounted values). These equated to incremental cost-effectiveness ratios of AU$101,649 per LY gained and AU$55,857 per QALY gained. A probabilistic sensitivity analysis demonstrated a likelihood of cost-effectiveness of 34.6%, assuming a willingness to pay threshold of AU$50,000 per QALY gained.

CONCLUSION

The likelihood of this program being cost-effective under a willingness to pay threshold AU$50,000 per QALY gained is 35%.

Restricted fluid bolus versus current practice in children with septic shock: the FiSh feasibility study and pilot RCT

BACKGROUND

There has been no randomised controlled trial (RCT) of fluid bolus therapy in paediatric sepsis in the developed world despite evidence that excess fluid may be associated with harm.

OBJECTIVES

To determine the feasibility of the Fluids in Shock (FiSh) trial - a RCT comparing restricted fluid bolus (10 ml/kg) with current practice (20 ml/kg) in children with septic shock in the UK.

DESIGN

(1) Qualitative feasibility study exploring parents' views about the pilot RCT. (2) Pilot RCT over a 9-month period, including integrated parental and staff perspectives study.

SETTING

(1) Recruitment took place across four NHS hospitals in England and on social media. (2) Recruitment took place across 13 NHS hospitals in England.

PARTICIPANTS

(1) Parents of children admitted to a UK hospital with presumed septic shock in the previous 3 years. (2) Children presenting to an emergency department with clinical suspicion of infection and shock after 20 ml/kg of fluid. Exclusion criteria were receipt of > 20 ml/kg of fluid, conditions requiring fluid restriction and the patient not for full active treatment (i.e. palliative care plan in place). Site staff and parents of children in the pilot were recruited to the perspectives study.

INTERVENTIONS

(1) None. (2) Children were randomly allocated (1 : 1) to 10- or 20-ml/kg fluid boluses every 15 minutes for 4 hours if in shock.

MAIN OUTCOME MEASURES

(1) Acceptability of FiSh trial, proposed consent model and potential outcome measures. (2) Outcomes were based on progression criteria, including recruitment and retention rates, protocol adherence and separation between the groups, and collection and distribution of potential outcome measures.

RESULTS

(1) Twenty-one parents were interviewed. All would have consented for the pilot study. (2) Seventy-five children were randomised, 40 to the 10-ml/kg fluid bolus group and 35 to the 20-ml/kg fluid bolus group. Two children were withdrawn. Although the anticipated recruitment rate was achieved, there was variability across the sites. Fifty-nine per cent of children in the 10-ml/kg fluid bolus group and 74% in the 20-ml/kg fluid bolus group required only a single trial bolus before shock resolved. The volume of fluid (in ml/kg) was 35% lower in the first hour and 44% lower over the 4-hour period in the 10-ml/kg fluid bolus group. Fluid boluses were delivered per protocol (volume and timing) for 79% of participants in the 10-ml/kg fluid bolus group and for 55% in the 20-ml/kg fluid bolus group, mainly as a result of delivery not being completed within 15 minutes. There were no deaths. Length of hospital stay, paediatric intensive care unit (PICU) transfers, and days alive and PICU free did not differ significantly between the groups. Two adverse events were reported in each group. A questionnaire was completed by 45 parents, 20 families and seven staff were interviewed and 20 staff participated in focus groups. Although a minority of site staff lacked equipoise in favour of more restricted boluses, all supported the trial.

CONCLUSIONS

Even though a successful feasibility and pilot RCT were conducted, participants were not as unwell as expected. A larger trial is not feasible in its current design in the UK.

FUTURE WORK

Further observational work is required to determine the epidemiology of severe childhood infection in the UK in the postvaccine era.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN15244462.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 22, No. 51. See the NIHR Journals Library website for further project information.

An Overview of Neisseria meningitidis

Neisseria meningitidis (the meningococcus) is a member of the normal nasopharyngeal microbiome in healthy individuals, but can cause septicemia and meningitis in susceptible individuals. In this chapter we provide an overview of the disease caused by N. meningitidis and the schemes used to type the meningococcus. We also review the adhesions, virulence factors, and phase variable genes that enable it to successfully colonize the human host. Finally, we outline the history and current status of meningococcal vaccines and highlight the importance of continued molecular investigation of the epidemiology and the structural analysis of the antigens of this pathogen to aid future vaccine development.

Costs of Invasive Meningococcal Disease: A Global Systematic Review

BACKGROUND

Invasive meningococcal disease remains a public health concern because of its rapid onset and significant risk of death and long-term disability. New meningococcal serogroup B and combination serogroup ACWY vaccines are being considered for publicly funded immunization programs in many countries. Contemporary costing data associated with invasive meningococcal disease are required to inform cost-effectiveness analyses.

OBJECTIVE

The objective of this study was to estimate costs and resource utilization associated with acute infection and the long-term care of invasive meningococcal disease.

DATA SOURCES AND METHODS

PubMed, EMBASE, The Cochrane Library, health economic databases, and electronically available conference abstracts were searched. Studies reporting any costs associated with acute infection and long-term sequelae of invasive meningococcal disease in English were included. All costs were converted into purchasing power parity-adjusted estimates [international dollars (I$)] using the Campbell and Cochrane Economics Methods Group and the Evidence for Policy and Practice Information and Coordinating Centre cost converter.

RESULTS

Fourteen studies met our eligibility criteria and were included. The mean costs of acute admission ranged from I$1629 to I$50,796, with an incremental cost of I$16,378. The mean length of hospital stay was reported to be 6-18 days in multiple studies. The average costs reported for readmissions ranged from I$7905 to I$15,908. Key variables such as the presence of sequelae were associated with higher hospitalization costs and longer inpatient stay. No studies estimated direct non-healthcare costs and productivity loss. Ten studies reported only unadjusted mean values without using appropriate statistical methods for adjustment.

CONCLUSIONS

Invasive meningococcal disease can result in substantial costs to healthcare systems. However, costing data on long-term follow-up and indirect costs used to populate health economic models are lacking.

An update of clinical experience with the quadrivalent meningococcal ACWY-CRM conjugate vaccine

INTRODUCTION

Menveo, quadrivalent meningococcal ACWY-CRM conjugate vaccine, was first licensed in 2010 in the United States and has a long track record of immunogenicity and safety in all age groups, including infants from 2 months of age.

AREAS COVERED

This review presents clinical and post-marketing experience with MenACWY-CRM from 32 studies conducted in 20 countries that included individuals aged from 2 months to 75 years.

EXPERT COMMENTARY

This decade has seen an increased number of countries reporting serogroup W ST-11 clonal complex outbreaks of invasive meningococcal disease. As infant vaccination programs targeting the meningococcus are reevaluated, the role of quadrivalent meningococcal vaccines including MenACWY-CRM will be expanded. MenACWY-CRM was immunogenic in all populations and age groups studied, regardless of country of origin. MenACWY-CRM can be coadministered with many routinely used infant, toddler and adolescent vaccines, and traveler vaccines in adults, allowing for flexible use within national immunization programs and recommendations. Antibody persistence has been demonstrated up to 5 years post vaccination in all age groups. Booster doses induced robust increases in antibody titers for all four serogroups, indicative of effective priming and induction of immunological memory. The acceptable safety profile of MenACWY-CRM has been confirmed in large post-marketing safety studies.

Protecting UK adolescents and adults against meningococcal serogroup B disease

INTRODUCTION

Meningococcal serogroup B disease (MenB) is endemic in the UK and continues to cause the majority of invasive meningococcal disease. Two broadly protective protein-based MenB vaccines are now licensed and available, both with wide age indications. Whilst the UK recently became the first country to routinely vaccinate infants against MenB, a recommendation has not yet been extended to older age groups who can also now benefit from these vaccines.

AREAS COVERED

This review summarizes the evidence supporting the rationale for adolescents and adults in the UK to consider MenB vaccination.

EXPERT COMMENTARY

Although MenB disease is rare, the UK reports one of the highest annual incidence rates within the European region, with over a third of cases occurring in those aged 10+ years. Overall, the case fatality rate following MenB disease in the UK is 4.2% but can be more than twice as high in teenagers and adults than in infants, and survivors are often left with life-changing disabling sequelae. MenB outbreaks are unpredictable and continue to occur in regions where it is endemic. These outbreaks often affect students attending school or university, with living on a campus being an important risk factor. Concerned individuals in this age group should consider MenB vaccination.

A qualitative feasibility study to inform a randomised controlled trial of fluid bolus therapy in septic shock

OBJECTIVE

The Fluids in Shock (FiSh) Trial proposes to evaluate whether restrictive fluid bolus therapy (10 mL/kg) is more beneficial than current recommended practice (20 mL/kg) in the resuscitation of children with septic shock in the UK. This qualitative feasibility study aimed to explore acceptability of the FiSh Trial, including research without prior consent (RWPC), potential barriers to recruitment and participant information for a pilot trial.

DESIGN

Qualitative interview study involving parents of children who had presented to a UK emergency department or been admitted to a paediatric intensive care unit with severe infection in the previous 3 years.

PARTICIPANTS

Twenty-one parents (seven bereaved) were interviewed 16 (median) months since their child's hospital admission (range: 1-41).

RESULTS

All parents said they would have provided consent for the use of their child's data in the FiSh Trial. The majority were unfamiliar with RWPC, yet supported its use. Parents were initially concerned about the change from currently recommended treatment, yet were reassured by explanations of the current evidence base, fluid bolus therapy and monitoring procedures. Parents made recommendations about the timing of the research discussion and content of participant information. Bereaved parents stated that recruiters should not discuss research immediately after a child's death, but supported a personalised postal 'opt-out' approach to consent.

CONCLUSIONS

Findings show that parents whose child has experienced severe infection supported the proposed FiSh Trial, including the use of RWPC. Parents' views informed the development of the pilot trial protocol and site staff training.

TRIAL REGISTRATION NUMBER

ISRCTN15244462-results.

Innate immune response to lipooligosaccharide: pivotal regulator of the pathobiology of invasive Neisseria meningitidis infections

Infections due to Neisseria meningitidis afflict more than one million people worldwide annually and cause death or disability in many survivors. The clinical course of invasive infections has been well studied, but our understanding of the cause of differences in patient outcomes has been limited because these are dependent on multiple factors including the response of the host, characteristics of the bacteria and interactions between the host and the bacteria. The meningococcus is a highly inflammatory organism, and the lipooligosaccharide (LOS) on the outer membrane is the most potent inflammatory molecule it expresses due to the interactions of the lipid A moiety of LOS with receptors of the innate immune system. We previously reported that increased phosphorylation of hexaacylated neisserial lipid A is correlated with greater inflammatory potential. Here we postulate that variability in lipid A phosphorylation can tip the balance of innate immune responses towards homeostatic tolerance or proinflammatory signaling that affects adaptive immune responses, causing disease with meningitis only, or septicemia with or without meningitis, respectively. Furthermore, we propose that studies of the relationship between bacterial virulence and gene expression should consider whether genetic variation could affect properties of biosynthetic enzymes resulting in LOS structural differences that alter disease pathobiology.

Deciphering the Burden of Meningococcal Disease: Conventional and Under-recognized Elements

Invasive meningococcal disease remains a substantial global public health burden despite being vaccine-preventable worldwide. More than one million cases are reported annually, with average fatality rates ranging from 10% to 40% depending on clinical presentation and geographic location. Survivors may suffer debilitating sequelae that reduce the quality of life for the patient and family members responsible for their care. Major financial burdens are associated with acute treatment and follow-up care, and outbreak management often places extensive financial strains on public health resources. Although the clinical and financial aspects of meningococcal disease burden are straightforward to quantify, other burdens such as lifelong cognitive deficits, psychological stress, adaptive measures for reintegration into society, familial impact, and legal costs are systematically overlooked. These and other facets of disease burden are therefore not systematically considered in cost-effectiveness analyses that public health authorities take into consideration when making decisions regarding vaccination programs. Changing the approach for measuring meningococcal disease burden is necessary to accurately understand the societal consequences of this devastating illness. In this article, the conventional and under-recognized burdens of meningococcal disease are presented and discussed.

N. meningitidis and TLR Polymorphisms: A Fascinating Immunomodulatory Network

N. meningitidis infections represent a global health problem that can lead to the development of serious permanent sequelae. Although the use of antibiotics and prevention via vaccination have reduced the incidence of meningococcal disease, our understanding regarding N. meningitidis pathogenesis is still limited, especially of those mechanisms responsible for IMD and fulminant or deadly septic shock. These severe clinical presentations occur in a limited number of subjects, whereas about 10% of healthy individuals are estimated to carry the bacteria as a commensal. Since TLR activation is involved in the defense against N. meningitidis, several studies have highlighted the association between host TLR SNPs and a higher susceptibility and severity of N. meningitidis infections. Moreover, TLR SNPs induced variations in immunological responses and in their persistence upon vaccination against meningococcal disease. In the absence of mass vaccination programs, the early identification of risk factors for meningococcal disease would be recommended in order to start immunization strategies and antibiotic treatment in those subjects carrying the risk variants. In addition, it could allow us to identify individuals with a higher risk for severe disease and sequelae in order to develop a personalized healthcare of high-risk subjects based on their genomic profile. In this review, we have illustrated important preliminary correlations between TLR variants and meningococcal susceptibility/severity and with vaccine-induced immune responses.

The Burden of Pediatric Invasive Meningococcal Disease in Spain (2008-2013)

BACKGROUND

Invasive meningococcal disease remains a rare infectious disease not only with high mortality but also with important morbidity. Until recently no universal vaccine existed against serogroup B, which explains most of the cases in settings like Europe. The objective of this study was to analyze the clinical course and sequelae of meningococcal disease in Spain.

METHODS

Retrospective review of all children younger than 15 years admitted to any of the 36 hospitals in the MENDICOS Spanish network (www.mendicos.org) with confirmed or probable invasive meningococcal disease in children between January 2008 and December 2013.

RESULTS

A total of 458 cases were identified across the country, most of them occurring in previously healthy children (91.5%; n = 419/458). Median (interquartile range) age was 1.7 (0.7 and 4.6) years, with 53.1% of the cases occurring in children younger than 2 years; 82.1% (n = 368) were laboratory confirmed cases; 95.2% (n = 256) of those serogrouped were serogroup B. The diagnosis was meningitis in 24.9% (n = 114) of the cases, sepsis in 37.1% (n = 170) and both in 38.0% (n = 174). Mean hospital length of stay was 11.6 (10.9) days; 79.2% (n = 354) of the patients required pediatric intensive care unit admission, with a mean pediatric intensive care unit stay of 3.9 (4.9) days; 3.5% (n = 16) died; 12.9% (n = 59) of the survivors were discharged with some kind of physical sequelae, mainly neurological (n = 23).

CONCLUSIONS

Serogroup B invasive meningococcal infection explains substantial morbidity and mortality in Spain, occurring mainly in infants. The recent availability of a vaccine against serogroup B may change this scenario. Given that the vast majority of the cases occur in otherwise healthy children, inclusion of the meningococcal B vaccine in the national immunization program should be carefully considered.

A Survey of Serum Bactericidal Antibodies against Neisseria meningitidis Serogroups A, C, W and Y in Adolescents and Adults in the Republic of Korea

Background

This descriptive epidemiological study aimed to assess the prevalence of serum bactericidal antibodies against Neisseria meningitidis serogroups A, C, W and Y in adolescents and adults in the Republic of Korea.

Materials and Methods

In total, 987 subjects aged 11-55 years from five geographical regions of Korea were included in the study. Human serum bactericidal assay (hSBA) was used to measure hSBA titres for serogroups A, C, W and Y. Percentages of subjects with hSBA titres ≥4 and ≥8, geometric mean titres (GMTs), and associated 95% confidence intervals (CIs), were estimated. Analysis was performed for the entire study population and stratified by age group or region. No statistical hypotheses were tested.

Results

The highest percentage of subjects with hSBA titres ≥8 was observed for serogroup W (74%), was similar for serogroups C (34%) and Y (36%), and was lowest for serogroup A (9%). The percentages of subjects with hSBA titres ≥4 were similar to those with hSBA titres ≥8 for all serogroups. GMTs were 2.56 µg/mL (serogroup A), 5.14 µg/mL (serogroup C), 22.63 µg/mL (serogroup W) and 5.28 µg/mL (serogroup Y). Similar trends in GMTs across serogroups were seen for individual regions and age groups. The highest GMTs for serogroups A, W and Y were recorded in the >19-29 years group, and for serogroup C in the >49-55 years group. Across all regions, GMTs were very similar for serogroups A, C and Y, while more variation was seen for serogroup W.

Conclusion

In the Korean population, among Neisseria meningitidis serogroups A, C, W and Y, serum bactericidal antibodies were most prevalent against serogroup W and least prevalent against serogroup A. These trends were maintained across age groups and regions. The highest GMTs for serogroups A, W and Y were observed in the >19-29 years group. The reasons behind the observed differences in prevalence of bactericidal antibodies against the serogroups are currently not understood, although carriage and cross-reactivity of the assay may be important influences.

Routinely vaccinating adolescents against meningococcus: targeting transmission & disease

Adolescents have the highest rates of meningococcal carriage and transmission. Interrupting the adolescent habitat in order to reduce carriage and transmission within adolescents and to other age groups could help to control meningococcal disease at a population level. Compared to immunization strategies restricted to young children, a strategy focused on adolescents may have more profound and long-lasting indirect impacts, and may be more cost effective. Despite challenges in reaching this age-group, experience with other vaccines show that high vaccine coverage of adolescents is attainable.

Competition between antagonistic complement factors for a single protein on N. meningitidis rules disease susceptibility

Genome-wide association studies have found variation within the complement factor H gene family links to host susceptibility to meningococcal disease caused by infection with Neisseria meningitidis (Davila et al., 2010). Mechanistic insights have been challenging since variation within this locus is complex and biological roles of the factor H-related proteins, unlike factor H, are incompletely understood. N. meningitidis subverts immune responses by hijacking a host-immune regulator, complement factor H (CFH), to the bacterial surface (Schneider et al., 2006; Madico et al., 2007; Schneider et al., 2009). We demonstrate that complement factor-H related 3 (CFHR3) promotes immune activation by acting as an antagonist of CFH. Conserved sequences between CFH and CFHR3 mean that the bacterium cannot sufficiently distinguish between these two serum proteins to allow it to hijack the regulator alone. The level of protection from complement attack achieved by circulating N. meningitidis therefore depends on the relative levels of CFH and CFHR3 in serum. These data may explain the association between genetic variation in both CFH and CFHR3 and susceptibility to meningococcal disease.

The clinical features and long-term sequelae of invasive meningococcal disease in children

We evaluated the outcome of invasive meningococcal disease in children <15 years of age (n = 181). Neisseria meningitidis serogroup B comprised 78% of bacterial isolates. Case fatality rate was 11.6%. In follow-up interviews (115/160 survivors, 72%), at least 1 long-term sequela was reported in 38/115 children (33%), including learning-academic difficulties (22.6%), hearing impairment (7%), neurologic (12.2%), behavioral (14.8%) and motor (10.4%) deficits.

Meningococcal serogroup Y emergence in Europe: high importance in some European regions in 2012

Neisseria meningitidis is differentiated into 12 distinct serogroups, of which A, B, C, W, X, and Y are medically most important and represent an important health problem in different parts of the world. The epidemiology of N. meningitidis is unpredictable over time and across geographic regions. Recent epidemiological surveillance has indicated an increase of serogroup Y invasive meningococcal disease in some parts of Europe as shown in the epidemiological data for 2010 and 2011 from various European countries previously published in this journal. (1)(,) (2) Here, data from 33 European countries is reported indicating that the emergence of serogroup Y continued in 2012 in various regions of Europe, especially in Scandinavia, while in Eastern and South-Eastern Europe the importance of serogroup Y remained low.