Multicenter surveillance of invasive meningococcal infections in children

Outcomes of Extracorporeal Life Support in Children with Meningococcal Septicemia: A Retrospective Cohort Study

Meningococcal disease is associated with high mortality despite aggressive antibiotic therapy and intensive care support. Patients may develop refractory hypotension and acute respiratory distress syndrome in which extracorporeal membrane oxygenation (ECMO) could serve as a life-saving rescue therapy. However, there is limited data regarding the outcomes of ECMO support in the setting of meningococcal disease. This retrospective analysis of prospectively collected data from Extracorporeal Life Support Organization registry (1989-2019) enrolled children (29 days-18 years old) with Neisseria meningitidis infection receiving ECMO for any support type and mode. A total of 122 patients underwent a single course of ECMO support, equating to 122 ECMO runs. The overall survival-to-discharge rate was 46.7%. Patients receiving pulmonary venovenous (VV) ECMO had the highest survival-to-discharge of 85.7%, while those receiving venoarterial (VA) ECMO for pulmonary indications had a survival of 32.4%. Patients receiving VA ECMO support for cardiac indications had a survival-to-discharge rate of 60.9%. Those needing extracorporeal cardiopulmonary resuscitation (ECPR) had a poor survival (14.3%). Hemorrhagic complications were common, occurring in 43.4% of patients, but not found to be associated with mortality (complication was present in 47.7% of deceased and 38.6% of survivors, p  = 0.31). Multivariable logistic regression analysis revealed that neurologic complications were associated with increased odds of mortality (odds ratio: 44.11; 95% confidence interval: 4.95-393.08). ECMO can be utilized as rescue therapy in children with refractory cardiopulmonary failure in setting of meningococcemia. Patients who require pulmonary VV or cardiac ECMO have the best ECMO outcomes. However, the use of ECMO in those suffering cardiac arrest (ECPR) should be undertaken with caution.

A database study of clinical and economic burden of invasive meningococcal disease in France

Objective

Invasive meningococcal disease (IMD) is life-threatening and associated with substantial morbidity and mortality. The study aimed to examine the clinical characteristics and hospital-based healthcare resource use and related costs following IMD diagnosis in France.

Methods

Patients admitted to hospitals due to IMD between 2014 and 2016 were selected from the French hospital discharge database (PMSI). Demographics, clinical outcomes and health utilization (HRU) during index hospitalization were described. HRU and costs during the follow-up period were also examined. A generalized linear model was applied to examine 1-year costs after index hospitalization adjusting for age, type of IMD and presence of sequelae at index hospitalization.

Results

A total of 1,344 patients were identified. About 30% cases were in children < 5 years old and 25% aged 10–24 years. Majority of patients presented as meningococcal meningitis (59%), 25% as meningococcaemia, and 9% both. The case fatality rate during the index hospitalization was 6%. About 15% of patients had at least one sequela at index hospital discharge. The median length of stay and the median cost of index hospitalization were 9 days and 8,045€, respectively. Patients with at least one sequela, with clinical manifestation as both meningitis and meningococcaemia, or aged 25 years and older were statistically significantly associated with higher costs than others.

Conclusion

IMD is unpredictable and can occur in all ages. The study highlights the severity and high health and economic burdens associated with the disease. The data underlines the importance of prevention against IMD through vaccination.

Real-world evidence of quadrivalent meningococcal conjugate vaccine safety in the United States: a systematic review

Two quadrivalent meningococcal conjugate vaccines (MenACWY) that prevent invasive meningococcal disease caused by N. meningitidis serogroups A, C, Y, and W have been licensed in the U.S. in the past 10-15 years. We systematically reviewed published studies conducted in the U.S. to evaluate the real-world safety evidence of meningococcal conjugate vaccines. We performed a literature search in PubMed of publications from 01/01/2005 to 02/29/2020 and identified 18 studies meeting inclusion criteria. Populations included high-risk persons aged 2 months to 10 years, adolescents/adults aged ≥11 years, pregnant populations, and hematopoietic cell transplant recipients. We extracted information about study setting, study design, exposure, outcomes, comparison group, follow-up/look back period, study population, sample size, available demographic/indication information, results, key conclusion, and reference. These published studies found no new significant safety concerns related to MenACWY. Consideration for future research includes a post-licensure safety evaluation of a new MenACWY product approved in April 2020.

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.

Clinical and economic burden of invasive meningococcal disease: Evidence from a large German claims database

BACKGROUND

Limited data is available to describe clinical characteristics, long-term outcomes, healthcare resource use and the attributable costs of invasive meningococcal disease (IMD) in Germany. We aimed to examine demographic and clinical characteristics as well as healthcare resource use and related costs.

METHODS

We conducted a retrospective cohort study based on the InGef database in patients with IMD between 2009 and 2015. Cases were identified based on hospital main discharge diagnoses of IMD. Demographics, clinical characteristics, 30-day and 1-year mortality as well as IMD-related complications and sequelae in IMD cases were examined. In addition, short and long-term costs and healthcare resource use in IMD cases were analyzed and compared to an age- and sex-matched control group without IMD.

RESULTS

The study population comprised 164 IMD cases between 2009 and 2015. The mean length of the IMD-related hospitalization was 13 days and 38% of all cases presented with meningitis only, 35% with sepsis only, 16% with both and 11% with other IMD. The 30-day and one-year mortality were 4.3% and 5.5%, respectively. Approximately 13% of IMD cases had documented IMD-related complications at hospital discharge and 24% suffered from sequelae during follow-up. The IMD-related hospitalization was associated with mean costs of € 9,620 (standard deviation: € 22,197). The difference of mean costs between IMD cases and matched non-IMD controls were € 267 in the first month and € 1,161 from one month to one year after discharged from IMD-related hospitalization. During the later follow-up period, the mean overall costs and costs associated with individual healthcare sectors were also higher for IMD cases without reaching statistical significance.

CONCLUSIONS

IMD resulted in severe complications and sequelae and was associated with extensive costs and increased healthcare resource use in Germany, especially in the first year after IMD diagnosis and due the IMD-related hospitalization.

Child with serogroup W135 primary meningococcal septic arthritis

Over the last decade, there has been a concerning increase in the number of invasive meningococcal serotype W infections in Europe. Although sepsis and meningitis are the most feared complications, focal complications of systemic disease such as pneumonia, pericarditis and arthritis can also occur. We present a rare case of isolated meningococcal W135 arthritis of the hip without invasive meningococcal disease in a 6-year-old patient.

A Meningococcal Outer Membrane Vesicle Vaccine with Overexpressed Mutant FHbp Elicits Higher Protective Antibody Responses in Infant Rhesus Macaques than a Licensed Serogroup B Vaccine

MenB-4C (Bexsero; GlaxoSmithKline Biologicals) is a licensed meningococcal vaccine for capsular B strains. The vaccine contains detergent-extracted outer membrane vesicles (dOMV) and three recombinant proteins, of which one is factor H binding protein (FHbp). In previous studies, overexpression of FHbp in native OMV (NOMV) with genetically attenuated endotoxin (LpxL1) and/or by the use of mutant FHbp antigens with low factor H (FH) binding increased serum bactericidal antibody (SBA) responses. In this study, we immunized 13 infant macaques with 2 doses of NOMV with overexpressed mutant (R41S) FHbp with low binding to macaque FH (NOMV-FHbp). Control macaques received MenB-4C (n = 13) or aluminum hydroxide adjuvant alone (n = 4). NOMV-FHbp elicited a 2-fold higher IgG anti-FHbp geometric mean titer (GMT) than MenB-4C (P = 0.003), and the anti-FHbp repertoire inhibited binding of FH to FHbp, whereas anti-FHbp antibodies to MenB-4C enhanced FH binding. MenB-4C elicited a 10-fold higher GMT against strain NZ98/254, which was used to prepare the dOMV component, whereas NOMV-FHbp elicited an 8-fold higher GMT against strain H44/76, which was the parent of the mutant NOMV-FHbp vaccine strain. Against four strains with PorA mismatched to both of the vaccines and different FHbp sequence variants, NOMV-FHbp elicited 6- to 14-fold higher SBA GMTs than MenB-4C (P ≤ 0.0002). Two of 13 macaques immunized with MenB-4C but 0 of 17 macaques immunized with NOMV-FHbp or adjuvant developed serum anti-FH autoantibodies (P = 0.18). Thus, the mutant NOMV-FHbp approach has the potential to elicit higher and broader SBA responses than a licensed group B vaccine that contains wild-type FHbp that binds FH. The mutant NOMV-FHbp also might pose less of a risk of eliciting anti-FH autoantibodies.IMPORTANCE There are two licensed meningococcal capsular B vaccines. Both contain recombinant factor H binding protein (FHbp), which can bind to host complement factor H (FH). The limitations of these vaccines include a lack of protection against some meningococcal strains and the potential to elicit autoantibodies to FH. We immunized infant macaques with a native outer membrane vesicle (NOMV) vaccine with genetically attenuated endotoxin and overproduced mutant FHbp with low binding to FH. The NOMV-FHbp vaccine stimulated higher levels of protective serum antibodies than a licensed meningococcal group B vaccine against five of six genetically diverse meningococcal strains tested. Two of 13 macaques immunized with the licensed vaccine, which contains FHbp that binds macaque FH, but 0 of 17 macaques given NOMV-FHbp or the negative control developed serum anti-FH autoantibodies Thus, in a relevant nonhuman primate model, the NOMV-FHbp vaccine elicited greater protective antibodies than the licensed vaccine and may pose less of a risk of anti-FH autoantibody.

Immunogenicity and Safety of a Quadrivalent Meningococcal ACWY-tetanus Toxoid Conjugate Vaccine 6 Years After MenC Priming as Toddlers

BACKGROUND

We assessed immunogenicity, antibody persistence and safety of the meningococcal serogroups A, C, W and Y-tetanus toxoid (TT) conjugate vaccine (MenACWY-TT) in children primed as toddlers with MenC vaccine.

METHODS

This open, multicenter extension study enrolled children 84-95 months of age who had received one dose of the combined Haemophilus influenzae type b (Hib)-MenC-TT conjugate vaccine (HibMenC group) or Hib-TT and monovalent MenC (MCC)-CRM197 vaccines (Hib+MCC group) at 12-18 months of age, in the primary study. All participants received one dose of MenACWY-TT. We assessed immunogenicity against MenA, MenC, MenW and MenY at 1 month and 2 years postvaccination by serum bactericidal assay using baby rabbit complement (rSBA). Safety and reactogenicity were evaluated.

RESULTS

Six years post-MenC vaccination, <20% of children retained rSBA-MenC titers ≥1:8. At 1 month post-MenACWY-TT vaccination, vaccine response rates against all serogroups were high for both groups with ≥97.1% of children having rSBA ≥1:8. Two years postvaccination, ≥63.6% of children retained rSBA-MenA ≥1:8, and ≥87.9% for other serogroups. Geometric mean titers for all serogroups declined at 2 years post-MenACWY-TT vaccination, but remained ≥13 times higher than prevaccination levels. For both groups, pain (≤58.5%), redness (≤51.4%) and fatigue (≤27.0%) were the most frequently reported adverse events. No serious adverse events were reported.

CONCLUSIONS

One dose of MenACWY-TT boosts protection against MenC in primed children, is safe and extends protection against MenA, MenW and MenY. Immunogenicity and safety were comparable in infants vaccinated with conjugated vaccine (HibMenC-TT) or the separate vaccines (Hib-TT and MCC-CRM197).

Parental awareness of Meningococcal B vaccines and willingness to vaccinate their teens

Background:

In the US, Meningococcal B (MenB) vaccines were first licensed in 2014. In 2015, the Advisory Committee on Immunization Practices recommended that parents of teens talk to their provider about receiving MenB vaccine, rather than issuing a routine recommendation. We assessed parental awareness of MenB vaccines and willingness to vaccinate their teens with MenB vaccines compared to MenACWY vaccines, which have been routinely recommended for many years.

Methods:

We surveyed parents of teens attending high school in 2017–18 during the Minnesota State Fair. Parents reported via iPad their knowledge of and concern about meningococcal disease and their awareness of and willingness to vaccinate with MenB and MenACWY vaccines. We assessed the relationship between meningococcal disease knowledge and concern, MenB and MenACWY vaccine awareness, and willingness to vaccinate with MenB and MenACWY using adjusted logistic regression.

Results:

Among 445 parents, the majority had not heard of the newly introduced MenB vaccines Bexsero^® (80.0%; 95% CI: 76.0–83.6) or Trumenba^® (82.0%; 95% CI: 78.1–85.5) or the MenACWY vaccines Menactra^® or Menveo^® (68.8%; 95% CI: 64.2–73.0). The majority were at least somewhat willing to vaccinate their teen with MenB vaccine (89.6%; 95% CI: 86.5, 92.3) and MenACWY vaccine (91.2%; 95% CI: 88.2, 93.7). Awareness of MenB vaccines (OR: 3.8; 95% CI: 1.2–12.2) and concern about meningococcal disease (OR: 3.1; 95% CI: 1.5–6.3) were significantly associated with willingness to vaccinate with MenB vaccine.

Conclusions:

Awareness of MenB vaccine is lacking among parents of teens but is an important predictor of willingness to vaccinate with the newly licensed MenB vaccines.

Adoption of Serogroup B Meningococcal Vaccine Recommendations

: media-1vid110.1542/5799875076001PEDS-VA_2018-0344Video Abstract BACKGROUND AND OBJECTIVES: In 2015, the Advisory Committee on Immunization Practices recommended that 16- to 23-year-olds may be vaccinated with the serogroup B meningococcal (MenB) vaccine on the basis of individual clinical decision-making (Category B). We assessed the following among US pediatricians and family physicians (FPs): (1) practices regarding MenB vaccine delivery, (2) factors influencing a decision to recommend the MenB vaccine, and (3) factors associated with discussing the MenB vaccine.

METHODS

We surveyed a nationally representative sample of pediatricians and FPs via e-mail and Internet from October 2016 to December 2016.

RESULTS

The response rate was 72% (660 of 916). During routine visits, 51% of pediatricians and 31% of FPs reported always or often discussing MenB vaccine. Among those who discussed often or always, 91% recommended vaccination; among those who never or rarely discussed, 11% recommended. We found that 73% of pediatricians and 41% of FPs currently administered the MenB vaccine. Although many providers reported not knowing about factors influencing recommendation decisions, MenB disease outbreaks (89%), disease incidence (62%), and effectiveness (52%), safety (48%), and duration of protection of MenB vaccine (39%) increased the likelihood of recommendation, whereas the Category B recommendation (45%) decreased likelihood. Those somewhat or not at all aware of the MenB vaccine (risk ratio 0.32 [95% confidence interval 0.25-0.41]) and those practicing in a health maintenance organization (0.39 [0.18-0.87]) were less likely, whereas those aware of disease outbreaks in their state (1.25 [1.08-1.45]) were more likely to discuss MenB vaccine.

CONCLUSIONS

Primary care physicians have significant gaps in knowledge about MenB disease and the MenB vaccine, and this appears to be a major driver of the decision not to discuss the vaccines.

Invasive Meningococcal Disease due to group C N. meningitidis ST11 (cc11): The Tuscany cluster 2015-2016

OBJECTIVES

To describe the cluster of MenC ST11 Invasive Meningococcal Disease (IMD) occurred in Tuscany in the years 2015-2016.

METHODS

A retrospective charts analysis of clinical, epidemiological and microbiological aspects of documented IMD was performed. Prognostic factors for death were evaluated.

RESULTS

Sixty-one patients with IMD in the 2015-2016 period were documented: 28 had meningococcemia, 24 meningitis plus meningococcemia and 9 meningitis. MenC ST11 (cc11) was identified in 48/54 (89%) of the tested strains. All patients, with the exception of three very early death, received timely and appropriate antibiotic therapy and, in selected case, adjunctive therapy with steroids and Pentaglobin®. Forty-one patients recovered (67.3%, mean age: 26 years), 7 had permanent sequelae (11.3%, mean age 31 years) and 13 died (21.3%; mean age: 46 years). In a multivariate analysis, septic shock, purpura fulminans and advanced age were negative prognostic factors, while emergency admittance to a tertiary-care, university hospital, positively influenced the survival rate. The epidemiological analysis of the cluster identified close contacts and recreational environments such as discos as hotspot for MenC transmission. After a massive vaccination campaign, the number of MenC cases reported in Tuscany in 2017 decreased to 10, with no death.

CONCLUSIONS

Vaccination campaign of key populations together with the need for rapid and qualified emergency care of the affected patients seems to be the main lesson learned by the MenC ST11 Tuscany epidemic.

An epidemic of meningococcal disease in children in North Norway in the 1970s and 1980s was dominated by a hypervirulent group B strain

AIM

We examined children hospitalised for invasive meningococcal disease, a leading cause of paediatric sepsis, in Troms County, North Norway, from 1973 to 2016, including the epidemic in the 1970s and 1980s.

METHODS

This study was a retrospective review of children under the age of 15 years who were hospitalised for meningococcal disease at the University Hospital of North Norway and Harstad Hospital. We studied hospital and bacteriological records to determine the incidence rates and phenotypes involved.

RESULTS

There were 300 cases under 15 years and an incidence rate of 17 per 100,000 cases for 1973-2016. This was broken down into the following: 1973-1980 (n = 130, 49), 1981-1990 (n = 129, 39), and 1991-2016 (n = 41, 4.7), respectively. There were 21 (7%) deaths. Phenotype B:15:P1.7,16 was more common than the other phenotypes in the epidemic period before 1990 than after 1990 (p = 0.02) and had a significantly lower mortality rate than the other phenotypes (p = 0.04). Later years showed a more heterogenous phenotype distribution. Serogroup B was the dominant serogroup.

CONCLUSION

The B:15:P1.7,6 strain was more prevalent during the Norwegian epidemic of invasive meningococcal disease, but had a significantly lower mortality rate. The phenotype distribution was more heterogeneous after 1990. The dominant serogroup was B.

Safety of Quadrivalent Meningococcal Conjugate Vaccine in 11- to 21-Year-Olds

BACKGROUND

Meningococcal conjugate vaccination is recommended in the United States. This study evaluates the safety of quadrivalent meningococcal conjugate vaccine in a cohort aged 11 to 21 years.

METHODS

This cohort study with self-controlled case-series analysis was conducted at Kaiser Permanente Southern California. Individuals receiving MenACWY-CRM, a quadrivalent meningococcal conjugate vaccine, during September 30, 2011 to June 30, 2013, were included. Twenty-six prespecified events of interest (EOIs), including neurologic, rheumatologic, hematologic, endocrine, renal, pediatric, and pediatric infectious disease EOIs, were identified through electronic health records 1 year after vaccination. Of these, 16 were reviewed by case review committees. Specific risk and comparison windows after vaccination were predefined for each EOI. The relative incidence (RI) and 95% confidence intervals (CIs) were estimated through conditional Poisson regression models, adjusted for seasonality.

RESULTS

This study included 48 899 vaccinated individuals. No cases were observed in the risk window for 14 of 26 EOIs. The RI for Bell's palsy, a case review committee-reviewed EOI, was statistically significant (adjusted RI: 2.9, 95% CI: 1.1-7.5). Stratified analyses demonstrated an increased risk for Bell's palsy in subjects receiving concomitant vaccines (RI = 5.0, 95% CI = 1.4-17.8), and no increased risk for those without concomitant vaccine (RI = 1.1, 95% CI = 0.2-5.5).

CONCLUSIONS

We observed a temporal association between occurrence of Bell's palsy and receipt of MenACWY-CRM concomitantly with other vaccines. The association needs further investigation as it could be due to chance, concomitant vaccination, or underlying medical history predisposing to Bell's palsy.

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.

Epidemiological impact and cost-effectiveness of introducing vaccination against serogroup B meningococcal disease in France

INTRODUCTION

Despite its low incidence in France, invasive serogroup B meningococcal disease remains a public health concern. A new vaccine against the disease, Bexsero(®), has been licensed in the EU. We studied the epidemiological impact and cost-effectiveness of routine vaccination using Bexsero(®) in order to inform the decision-making process regarding its potential inclusion in the vaccination schedule.

METHODS

A multi-generational Markov model was used. Time horizon was set to 100 years. Five vaccination strategies were evaluated: infants at 3, 5, 6 and 13 months, toddlers at 13, 15 and 27 months and adolescents at 15 years provided 2 doses one month apart. A booster dose at 15 years old and a catch-up for 15 years old subjects during the first 15 years of the programme were added to the infant and toddler strategies. Costs per QALY gained were computed from a restricted societal perspective including direct costs only. Herd immunity was simulated in an alternative base-case scenario and sensitivity analyses.

RESULTS

In the base-case analysis without herd immunity and with all cohorts vaccinated, at € 40 per vaccine dose, routine infant vaccination would provide the lowest cost per QALY gained (€ 380,973) despite only preventing 18% of cases. Under the assumption of herd immunity, the adolescent vaccination would provide the lowest cost per QALY gained (€ 135,902) preventing 24% of cases. Infant vaccination with a late booster and catch-up would prevent 51% of cases with a cost of € 188,511 per QALY gained.

CONCLUSIONS

Given current meningococcal epidemiology in France and the available data on the protection provided by Bexsero(®), our modelling work showed that routine vaccination against serogroup B meningococcal disease is not cost-effective.

Vaccines for Prevention of Group B Meningococcal Disease: Not Your Father's Vaccines

For decades, there was no licensed vaccine for prevention of endemic capsular group B meningococcal disease, despite the availability of vaccines for prevention of the other most common meningococcal capsular groups. Recently, however, two new vaccines have been licensed for prevention of group B disease. Although immunogenic and considered to have an acceptable safety profile, there are many scientific unknowns about these vaccines, including effectiveness against antigenically diverse endemic meningococcal strains; duration of protection; whether they provide any herd protection; and whether there will be meningococcal antigenic changes that will diminish effectiveness over time. In addition, these vaccines present societal dilemmas that could influence how they are used in the U.S., including high vaccine cost in the face of a historically low incidence of meningococcal disease. These issues are discussed in this review.

Global incidence of serogroup B invasive meningococcal disease: a systematic review

Use of recently licensed vaccines against Neisseria meningitidis serogroup B (NmB) will depend partly on disease burden estimates. We systematically reviewed NmB incidence and mortality worldwide between January, 2000, and March, 2015, incorporating data from 37 articles and 12 websites. Most countries had a yearly invasive NmB incidence of less than 2 per 100,000 people. Within these relatively low incidence rates (compared with common causes of invasive bacterial diseases), substantial variation was detected between countries, with a notably higher incidence in Australia, Europe, North America, and South America. China and India had reports only of sporadic cases, and except for South Africa, sub-Saharan Africa showed a near absence of disease. In countries with consistently collected data, NmB incidence has tended to decrease, even as the proportion of invasive meningococcal disease cases caused by serogroup B has increased. With few exceptions, case-fatality ratios were fairly consistent, ranging between 3% and 10%. In high-income countries, incidence rates of NmB were relatively low compared with other vaccine-preventable diseases and might be decreasing. High case-fatality ratios, substantial disease-related morbidity, and the threat of outbreaks could nevertheless make NmB an attractive target for preventive and reactive immunisation programmes. The low availability of data from low-income and middle-income countries suggests the need for improved surveillance before vaccination strategies are designed.

Vaccines for prevention of group B meningococcal disease: Not your father's vaccines

For decades, there was no licensed vaccine for prevention of endemic capsular group B meningococcal disease, despite the availability of vaccines for prevention of the other most common meningococcal capsular groups. Recently, however, two new vaccines have been licensed for prevention of group B disease. Although immunogenic and considered to have an acceptable safety profile, there are many scientific unknowns about these vaccines, including effectiveness against antigenically diverse endemic meningococcal strains; duration of protection; whether they provide any herd protection; and whether there will be meningococcal antigenic changes that will diminish effectiveness over time. In addition, these vaccines present societal dilemmas that could influence how they are used in the U.S., including high vaccine cost in the face of a historically low incidence of meningococcal disease. These issues are discussed in this review.

Binding of complement factor H to PorB3 and NspA enhances resistance of Neisseria meningitidis to anti-factor H binding protein bactericidal activity

Among 25 serogroup B Neisseria meningitidis clinical isolates, we identified four (16%) with high factor H binding protein (FHbp) expression that were resistant to complement-mediated bactericidal activity of sera from mice immunized with recombinant FHbp vaccines. Two of the four isolates had evidence of human FH-dependent complement downregulation independent of FHbp. Since alternative complement pathway recruitment is critical for anti-FHbp bactericidal activity, we hypothesized that in these two isolates binding of FH to ligands other than FHbp contributes to anti-FHbp bactericidal resistance. Knocking out NspA, a known meningococcal FH ligand, converted both resistant isolates to anti-FHbp susceptible isolates. The addition of a nonbactericidal anti-NspA monoclonal antibody to the bactericidal reaction also increased anti-FHbp bactericidal activity. To identify a role for FH ligands other than NspA or FHbp in resistance, we created double NspA/FHbp knockout mutants. Mutants from both resistant isolates bound 10-fold more recombinant human FH domains 6 and 7 fused to Fc than double knockout mutants prepared from two sensitive meningococcal isolates. In light of recent studies showing functional FH-PorB2 interactions, we hypothesized that PorB3 from the resistant isolates recruited FH. Allelic exchange of porB3 from a resistant isolate to a sensitive isolate increased resistance of the sensitive isolate to anti-FHbp bactericidal activity (and vice versa). Thus, some PorB3 variants functionally bind human FH, which in the presence of NspA enhances anti-FHbp resistance. Combining anti-NspA antibodies with anti-FHbp antibodies can overcome resistance. Meningococcal vaccines that target both NspA and FHbp are likely to confer greater protection than either antigen alone.

Altered neutrophil counts at diagnosis of invasive meningococcal infection in children

BACKGROUND

Invasive meningococcal infections can be devastating. Substantial endotoxemia releases mature and immature neutrophils. Endothelial margination of mature neutrophils may increase the immature-to-total neutrophil ratio (ITR). These changes have not been previously well-described in invasive meningococcal disease.

METHODS

Using 2001 to 2011 data from the US Multicenter Meningococcal Surveillance Study, the diagnostic sensitivity and clinical correlates of white blood cell count, absolute neutrophil count (ANC), immature neutrophil count (INC) and ITR were evaluated alone and in combination at the time of diagnosis of invasive meningococcal disease.

RESULTS

Two hundred sixteen patients were evaluated: meningococcemia (65), meningitis (145) and other foci (6). ANC ≤1000/mm(3) or ≥10,000/mm(3) was present in 137 (63%), INC ≥500/mm(3) in 170 (79%) and ITR ≥0.20 in 139 (64%). One or more of these 3 criteria were met in 204 of the 216 (94%). Results were similar for meningococcemia and meningitis subgroups. All 13 cases with mildest disease met 1 or more of the 3 criteria. Eight children presented with ANCs <1000/mm(3): 3 of them died and a fourth required partial amputation in all 4 limbs.

CONCLUSIONS

Invasive meningococcal disease is characterized by striking abnormalities in ANC, INC and/or ITR. Neutropenia was associated with a poor prognosis. Notably, without INCs, 37% of cases would have been missed. Automated methods not measuring immature white blood cells should be avoided when assessing febrile children. Serious infection should be considered when counts meet any of the 3 criteria.

Prevention of meningococcal infections in the first 2 years of life

The spectrum of disease caused by Neisseria meningitidis includes bacteremia, fulminant sepsis (meningococcemia), meningitis, and pneumonia. The incidence of meningococcal infection has long been higher in infancy than adolescents or adults older than 65 years (a third group with an increased risk based on age). Five meningococcal serogroups (A, B, C, Y, and W135) cause the great majority of human disease. Serogroup B strains cause about two-thirds of disease in children younger than 6 years. For this reason, new meningococcal vaccine formulations have been developed and evaluated in children younger than 2 years. Of four meningococcal vaccines currently licensed in the United States, two conjugate products, (MenACWY-D [Menactra], Sanofi Pasteur; HibMenCY-TT [MenHibrix], GlaxoSmithKline), are recommended for infants and toddlers younger than 2 years who have an increased risk for invasive meningococcal disease. High-risk conditions are complement deficiencies, community outbreaks, functional or anatomic asplenia, and travel to high-risk areas in which serogroup A infection is prevalent. Recommendations vary by age, dosing, and indication between these two products. Both licensed products are immunogenic and have side-effect profiles that are considered safe for use. In most cases, concomitant use with other recommended childhood vaccines does not interfere with responses to these vaccines. As of yet, there has not been universal adoption of this immunization in the infant population by parents or providers. Factors that weigh against the implementation of a national routine infant program include the prevention of only 40 to 50 meningococcal cases, two to four deaths per year, and a relatively low case fatality among infants. Some argue that costs should not be considered a barrier because infant deaths and morbidity would be prevented. The availability of a serogroup B vaccine would improve impact and cost-effectiveness of a routine infant meningococcal vaccine program. Debate over the implementation of routine infant meningococcal vaccination in the United States is ongoing. This review focuses on vaccines for the prevention of N. meningitidis infection in infants and young toddlers in the first 2 years of life.

Invasive meningococcal infection: analysis of 110 cases from a tertiary care centre in North East India

OBJECTIVES

To report an outbreak of invasive meningococcal disease from Meghalaya, in the north east India, from January 2008 through June 2009.

METHODS

Retrospective review of case sheets was done. One hundred ten patients with invasive meningococcal disease were included for the study.

RESULTS

Of the total patients, 61.8 % were boys and 38.2 % were girls (boy to girl ratio = 1.62:1). The average age of presentation was 8.48 ± 5.09 y. Meningococcal meningitis was seen in 61.8 % of cases, meningococcemia in 20 % and 18.2 % had both. Fever was the most common manifestation (100 %) followed by meningeal signs (78.2 %), headache (56.4 %), vomiting (53.6 %), shock (38.2 %), low Glasgow coma scale (GCS) (25.5 %), purpura and rashes (23.6 %), seizures (9.1 %), abdominal symptoms (4.5 %), irritability and excessive crying (4.5 %) and bulging anterior fontanalle (23 %) in those below 18 mo of age. Raised intracranial pressure (ICP) was the most common complication (28.2 %) followed by coagulopathy (16.4 %), hepatopathy (10 %), herpes labialis (9.1 %), syndrome of inappropriate ADH secretion (SIADH) (8 %), pneumonia (7 %), arthritis (6 %), purpura fulminans, respiratory failure, sixth nerve palsy and diabetes insipidus in 4.5 % each, subdural empyema, optic neuritis, ARDS and ARF in 1.8 % each, cerebral salt wasting syndrome, third nerve palsy, cerebritis and hearing impairment in 0.9 % each. Culture was positive in 35.5 %. Patients were treated initially with ceftriaxone and dexamethasone but later on with chloramphenicol due to clinical drug resistance. Mortality was 6.4 %.

CONCLUSIONS

This is the first epidemic report of invasive meningococcal disease from the north east India. Chloramphenicol acts well in areas with penicillin or cephalosporin resistance. Mortality reduces significantly with early diagnosis and prompt intervention.

Dynamics of childhood invasive meningococcal disease in Israel during a 22-year period (1989-2010)

AIM

To describe the dynamics in the incidence of childhood invasive meningococcal disease (IMD) in Israel during a 22-year period (1989-2010).

METHODS

A longitudinal prospective surveillance in all 27 medical centers with pediatric services in Israel. All cases of children <15 years old with positive blood/cerebrospinal fluid (CSF) culture for Neisseria meningitidis were reported. Demographic, clinical, and bacteriological data were recorded. Meningococcal vaccine was not routinely given to Israeli children during the study period.

RESULTS

The mean age ± standard deviation (SD) among the 743 cases was 40.7 ± 40.2 months. The mean yearly incidence/100,000 was 2.0 ± 0.8. Age-specific incidences were 8.7 ± 2.8, 2.9 ± 1.5, and 0.8 ± 0.5 for children <1, 1-4, and >4 years old, respectively. The overall incidence decreased significantly from 3.7 in 1989 to 1.5 in 2010. Meningitis constituted 69.2 % of all cases. The most common serogroups were: B (76.9 %), C (10.9 %), Y (8.0 %), and W(135) (2.9 %). 78.6 % of all serogroup B isolates were from children <5 years old (p < 0.01). Serogroup C was found mainly in children ≥5 years old (63.4 %). The case fatality rates (CFRs) for children <1, 1-4, >4 years old, and the total study population were 9.2, 12.3, 7.7, and 9.9 %, respectively. CFRs were higher for children without meningitis (14.9 %) compared to children with meningitis (7.9 %) (p < 0.01).

CONCLUSIONS

Overall, and for serogroups B and W135, childhood IMD rates decreased significantly in Israel during the study period, without routine vaccine usage. The most common serogroup in all age groups was B, which was most prevalent in children <5 years old. No change in the trend of the overall CFR was noted during the study period.

The disease burden of invasive meningococcal serogroup B disease in Canada

BACKGROUND

Invasive meningococcal disease remains a rare but deadly infection in Canada. New serogroup B vaccines may offer the potential for prevention and control. This report examines the disease burden caused by serogroup B invasive meningococcal infections.

METHODS

From 2002 to 2011, active, population-based metropolitan area surveillance for adult and pediatric hospital admissions for adult and pediatric hospital admissions for laboratory-confirmed infection with Neisseria meningitidis, was conducted by the 12 centers of the Canadian Immunization Monitoring Program, Active.

RESULTS

A total of 769 invasive meningococcal cases occurred from 2002 to 2011; 54% (n = 413) in children with a peak incidence of 6.16 (95% confidence interval: 3.18-10.76) per 100,000 in children aged <1 year in 2009. Serogroup B accounted for the largest proportion of cases and had the highest incidence of all serogroups across all ages, with a peak incidence of 0.31 (0.23-0.40) per 100,000 in 2007. Serogroup B case fatality rate was 4.3% in children, and 21% of pediatric survivors had sequelae. B:17:P1.19 ST-269 was the most frequently detected antigenic type.

CONCLUSIONS

Serogroup B invasive meningococcal infections caused substantial morbidity and mortality and are the leading cause of invasive meningococcal disease in Canada. The proportion of cases potentially preventable with the new serogroup B vaccines should be evaluated to determine whether universal immunization programs are warranted.

MenACWY-TT vaccine for active immunization against invasive meningococcal disease

Meningococcal disease remains a significant global cause of morbidity and mortality despite the availability of polysaccharide and conjugate vaccines. The implementation of monovalent meningococcal serogroup C vaccine in developed countries has significantly decreased the incidence of meningococcal disease, while the recent introduction of monovalent serogroup A conjugate vaccine in the African meningitis belt aims to reduce the incidence of high endemic disease in this area. Three quadrivalent meningococcal vaccines have already been licensed; a polysaccharide (MenACWY-PS) and two conjugated (MenACWY-DT and MenACWY-CRM) vaccines. An investigational MenACWY-TT vaccine is described in this article. Clinical trials in infants older than 9 months of age, toddlers, children, adolescents and adults have indicated that this vaccine is well tolerated and immunogenic. The inclusion of a spacer molecule coupled with the polysaccharide (for serogroups A and C) and tetanus toxoid as the carrier protein aims to elicit robust immune responses. The tolerability of this vaccine is comparable to that of polysaccharide quadrivalent vaccines and monovalent meningococcal serogroup C vaccines. More importantly, the immunogenicity, antibody persistence and induction of immune memory aim to provide protection to a wide range of susceptible subjects.

Meningococcal disease: clinical presentation and sequelae

The clinical spectrum of invasive meningococcal disease is diverse with meningitis and/or septicaemia being the commonest modes of presentation. The severity of manifestations of meningococcal infection ranges from bacteraemia, associated with mild non-specific symptoms, to fulminant sepsis with multiorgan failure and death in approximately 10-15% of cases. Localised infections (such as conjunctivitis or septic arthritis) as well as chronic disease may be the sole clinical manifestations but can also lead to disseminated fulminant disease. Among survivors, disabling long-term sequelae can complicate meningococcal disease and result in potentially devastating effects on the quality of life of survivors, most of whom are infants, children and adolescents. The only rational approach to the prevention of meningococcal disease and the associated human suffering is through vaccination.

Formulation of meningococcal capsular polysaccharide vaccine-loaded microparticles with robust innate immune recognition

Neisseria meningitidis is a leading cause of bacterial meningitis and sepsis associated with a high mortality rate. Capsular polysaccharides (CPSs) are a major virulence factor and form the basis for serogroup designation and protective vaccines. The current polysaccharide meningococcal vaccines are available but are very expensive and require chemical conjugation. Here, we report a novel meningococcal vaccine formulation consisting of meningococcal CPS polymers encapsulated in albumin-based biodegradable microparticles that slowly release antigen and induce robust innate immune responses. Vaccines that elicit innate immunity are reported to have enhanced and protective adaptive immune responses. In this study, the meningococcal CPS-loaded microparticles, but not the empty microparticles, induced the release of IL-8, TNF-α and IL-1β, enhanced phagocytic capacity and induced robust autophagy in macrophages. The novel meningococcal vaccine microparticles are robustly taken up by macrophages and elicit strong innate immune responses that enhance antigen presentation which is a prerequisite for inducing adaptive immunity.

Consensus recommendation for meningococcal disease prevention in children and adolescents in the Middle East region

Facing the availability of the new generation of quadrivalent meningococcal conjugate vaccines (Menveo®, Menactra® and others pending for license) and their recent implementation in Saudi Arabia, experts from 11 countries of the Middle East region met at a “Meningococcal Leadership Forum” (MLF), which took place in May 2010 in Dubai. The participants of the conference discussed the importance of introducing the concept of conjugate vaccines – especially for children and adolescents – and elaborated a consensus recommendation to support healthcare professionals and decision makers with their expertise. In experts’ opinion, conjugate vaccines are the best choice for the prevention of meningococcal disease caused by serogroups A, C, W-135 and Y. As quadrivalent meningococcal conjugate vaccines are registered and available in the Middle East region, they should replace plain polysaccharide vaccines and be integrated in pediatric and adolescent vaccination schedules, including infant vaccination concomitantly with basic EPI vaccines when licensed.

Meningococcal disease serogroup C

Despite current advances in antibiotic therapy and vaccines, meningococcal disease serogroup C (MDC) remains a serious threat to global health, particularly in countries in North and Latin America, Europe, and Asia. MDC is a leading cause of morbidity, mortality, and neurological sequelae and it is a heavy economic burden. At the individual level, despite advances in antibiotics and supportive therapies, case fatality rate remains nearly 10% and severe neurological sequelae are frequent. At the population level, prevention and control of infection is more challenging. The main approaches include health education, providing information to the public, specific treatment, chemoprophylaxis, and the use of vaccines. Plain and conjugate meningococcal C polysaccharide vaccines are considered safe, are well tolerated, and have been used successfully for over 30 years. Most high-income countries use vaccination as a part of public health strategies, and different meningococcal C vaccination schedules have proven to be effective in reducing incidence. This is particularly so with conjugate vaccines, which have been found to induce immunogenicity in infants (the age group with the highest incidence rates of disease), stimulate immunologic memory, have longer effects, not lead to hyporesponsiveness with repeated dosing, and decrease acquisition of nasopharyngeal carriage, inducing herd immunity. Antibiotics are considered a cornerstone of MDC treatment and must be administered empirically as soon as possible. The choice of which antibiotic to use should be made based on local antibiotic resistance, availability, and circulating strains. Excellent options for a 7-day course are penicillin, ampicillin, chloramphenicol, and third-generation cephalosporins (ceftriaxone and cefotaxime) intravenously, although the latter are considerably more expensive than the others. The use of steroids as adjunctive therapy for MDC is still controversial and remains a topic of debate. A combination of all of the aforementioned approaches is useful in the prevention and control of MDC, and each country should tailor its public health policy to its own particular needs and knowledge of disease burden.

Haemophilus influenzae type b-Neisseria meningitidis serogroups C and Y tetanus toxoid conjugate vaccine for infants and toddlers

The highest rates of invasive meningococcal disease occur in children under 2 years of age, yet as of early 2011 no vaccine was licensed for the youngest infants. However, a novel vaccine consisting of capsular polysaccharides from Haemophilus influenzae type b (Hib) and Neisseria meningitidis serogroups C and Y conjugated to tetanus toxoid (HibMenCY-TT; MenHibrix, GlaxoSmithKline) is in the late stages of development. In clinical trials involving more than 7800 children, HibMenCY-TT was shown to be safe and immunogenic when administered at 2, 4, 6 and 12-15 months of age. Anti-polyribosylribitol phosphate antibody responses were noninferior to those elicited by licensed monovalent Hib vaccines, and most vaccinees developed bactericidal antibodies against N. meningitidis serogroups C and Y. The majority of subjects retained antibody responses as far as 3 years after vaccination. If licensed, HibMenCY-TT not only represents an incremental option for protection against invasive Hib, but also has the potential to prevent invasive meningococcal disease without increasing the number of injections.

Neisseria meningitidis: biology, microbiology, and epidemiology

Neisseria meningitidis (the meningococcus) causes significant morbidity and mortality in children and young adults worldwide through epidemic or sporadic meningitis and/or septicemia. In this review, we describe the biology, microbiology, and epidemiology of this exclusive human pathogen. N.meningitidis is a fastidious, encapsulated, aerobic gram-negative diplococcus. Colonies are positive by the oxidase test and most strains utilize maltose. The phenotypic classification of meningococci, based on structural differences in capsular polysaccharide, lipooligosaccharide (LOS) and outer membrane proteins, is now complemented by genome sequence typing (ST). The epidemiological profile of N. meningitidis is variable in different populations and over time and virulence of the meningococcus is based on a transformable/plastic genome and expression of certain capsular polysaccharides (serogroups A, B, C, W-135, Y and X) and non-capsular antigens. N. meningitidis colonizes mucosal surfaces using a multifactorial process involving pili, twitching motility, LOS, opacity associated, and other surface proteins. Certain clonal groups have an increased capacity to gain access to the blood, evade innate immune responses, multiply, and cause systemic disease. Although new vaccines hold great promise, meningococcal infection continues to be reported in both developed and developing countries, where universal vaccine coverage is absent and antibiotic resistance increasingly more common.

Surveillance for invasive meningococcal disease in children, US-Mexico border, 2005-2008

We reviewed confirmed cases of pediatric invasive meningococcal disease in Tijuana, Mexico, and San Diego County, California, USA, during 2005–2008. The overall incidence and fatality rate observed in Tijuana were similar to those found in the US, and serogroup distribution suggests that most cases in Tijuana are vaccine preventable.

Profile of serogroup Y meningococcal infections in Canada: Implications for vaccine selection

Canada is a leader in establishing routine infant immunization programs against meningococcal C disease. Currently, all provinces have routine programs to provide meningococcal C conjugate vaccines to infants and children. The result of the existing programs has been a decrease in serogroup C incidence. The second most common vaccine-preventable serogroup in Canada is serogroup Y, the incidence of which has been stable. The availability of a quadrivalent conjugate vaccine against serogroups A, C, Y and W135 focuses attention on serogroup Y disease as it becomes relatively more prominent as a cause of vaccine-preventable invasive meningococcal disease. This vaccine was licensed in November 2006 but is not routinely used except in Nunavut, New Brunswick and Prince Edward Island. To allow a better understanding of the 'value added' by a serogroup Y-containing vaccine, it is necessary to have a contemporary profile of Y disease in Canada. In the present paper, recent surveillance data on invasive meningococcal disease across Canada are summarized.

The Global Meningococcal Initiative: recommendations for reducing the global burden of meningococcal disease

The Global Meningococcal Initiative (GMI) is composed of an international group of scientists, clinicians and public health officials with expertise in meningococcal immunology, epidemiology and prevention. The primary goal of the GMI is the promotion of the global prevention of invasive meningococcal disease through education and research. The GMI members reviewed global meningococcal disease epidemiology, immunization strategies, and research needs. Over the past decade, substantial advances in meningococcal vaccine development have occurred and much has been learned about prevention from countries that have incorporated meningococcal vaccines into their immunization programs. The burden of meningococcal disease is unknown for many parts of the world because of inadequate surveillance, which severely hampers evidence-based immunization policy. As the field of meningococcal vaccine development advances, global surveillance for meningococcal disease needs to be strengthened in many regions of the world. For countries with meningococcal vaccination policies, research on vaccine effectiveness and impact, including indirect effects, is crucial for informing policy decisions. Each country needs to tailor meningococcal vaccination policy according to individual country needs and knowledge of disease burden. Innovative approaches are needed to introduce and sustain meningococcal vaccination programs in resource-poor settings with a high incidence of meningococcal disease.

Some of the Meningococcal Meningitis in Qatar: Epidemiology, clinical and laboratory features

To define the demographic, clinical and laboratory features, methods of diagnosis and outcome, in patients with meningococcal meningitis in Qatar, records were reviewed retrospectively to 25 patients (21 male, 4 female; mean age 24 years) treated for meningococcal meningitis at the Hamad Medical Corporation (HMC) between 1992 and 2008). Most (88%) were expatriates. The most common presenting symptoms were fever, vomiting, headache and altered consciousness. Neck stiffness and impaired level of consciousness were the most common signs. Elevated WBC, elevated protein and low glucose in CSF were present in 95.6%, 84% and 80% of cases respectively. Positive CSF Grainstain showing gram negative diplococci and culture growing N. meningitidis in CSF and blood were seen in 64%, 44% and 72.7% of cases respectively. The most common serotypes were Groups A and W 13 5 accounting for 50% and 25% respectively. 15.8% of isolates were intermediately resistant to penicillin, while all were sensitive to ceftriaxone. One patient (4%) died and 24 (96%) survived. Six of those who survived developed neurologic sequelae. Meningococcal meningitis remains uncommon in Qatar but the incidence has increased markedly recently especially among expatriates. Because the clinical features of the disease are non-specific, a high index of suspicion is essential for early diagnosis. Empirical treatment with ceftriaxone in a patient with suspected meningococcal meningitis seems prudent to avoid an unfavorable outcome.

Impaired immunogenicity of a meningococcal factor H-binding protein vaccine engineered to eliminate factor h binding

Meningococcal factor H-binding protein (fHbp) is a promising antigen that is part of two vaccines in clinical development. The protein specifically binds human complement factor H (fH), which downregulates complement activation on the bacterial surface and enables the organism to evade host defenses. In humans, the vaccine antigen forms a complex with fH, which may affect anti-fHbp antibody repertoire and decrease serum bactericidal activity by covering important fHbp epitopes. In a recent study, fHbp residues in contact with fH were identified from a crystal structure. Two fHbp glutamate residues that mediated ion-pair interactions with fH were replaced with alanine, and the resulting E218A/E239A mutant no longer bound the fH fragment. In the present study, we generated the E218A/E239A mutant recombinant protein and confirmed the lack of fH binding. By enzyme-linked immunosorbent assay (ELISA), the mutant fHbp showed similar respective concentration-dependent inhibition of binding of four bactericidal anti-fHbp monoclonal antibodies (MAbs) to fHbp, compared with inhibition by the soluble wild-type protein. In two mouse strains, the mutant fHbp elicited up to 4-fold-lower IgG anti-fHbp antibody titers and up to 20-fold-lower serum bactericidal titers than those elicited by the wild-type fHbp vaccine. Thus, although introduction of the two alanine substitutions to eliminate fH binding did not appear to destabilize the molecule globally, the mutations resulted in decreased immunogenicity in mouse models in which neither the mutant nor the wild-type control vaccine bound fH. These results cast doubt on the vaccine potential in humans of this mutant fHbp.