Invasive meningococcal disease in the 21st century—an update for the clinician

Impact of Meningococcal ACWY Vaccination Program during 2017-18 Epidemic, Western Australia, Australia

The rising incidence of invasive meningococcal disease (IMD) caused by Neisseria meningitidis serogroup W in Western Australia, Australia, presents challenges for prevention. We assessed the effects of a quadrivalent meningococcal vaccination program using 2012-2020 IMD notification data. Notification rates peaked at 1.8/100,000 population in 2017; rates among Aboriginal and Torres Strait Islander populations were 7 times higher than for other populations. Serogroup W disease exhibited atypical manifestations and increased severity. Of 216 cases, 20 IMD-related deaths occurred; most (19/20) were in unvaccinated persons. After the 2017-2018 targeted vaccination program, notification rates decreased from 1.6/100,000 population in 2018 to 0.9/100,000 population in 2019 and continued to decline in 2020. Vaccine effectiveness (in the 1-4 years age group) using the screening method was 93.6% (95% CI 50.1%-99.2%) in 2018 and 92.5% (95% CI 28.2%-99.2%) in 2019. Strategic planning and prompt implementation of targeted vaccination programs effectively reduce IMD.

Immunogenicity of the Conjugate Meningococcal ACWY-TT Vaccine in Children and Adolescents Living with HIV

BACKGROUND

Children and adolescents living with HIV (CALHIV) are at high risk of meningococcal infections and may present lower immune responses to vaccines. The objectives of this study were to assess the immunogenicity of the quadrivalent Men ACWY-TT vaccine (Nimenrix®) in CALHIV after a two-dose schedule and to describe possible HIV-related factors that may affect the immunogenic response.

METHODS

A multicenter prospective study was designed, including CALHIV followed in five hospitals in Madrid, between 2019 and 2021. Two doses of the Men ACWY-TT vaccine were administered. Serum bactericidal antibody (SBA) assays using rabbit complement (rSBA) against serogroups C, W, and Y were used to determine seroprotection and vaccine response (the proportion achieving a putative protective titer of ≥eight or a ≥four-fold rise in titer from baseline). Serum was collected at baseline, and at 3 and 12 months after vaccination.

RESULTS

There were 29 CALHIV included, 76% of whom were perinatally infected. All were receiving TAR and presented a good immunovirological and clinical status overall. At baseline, 45% of CALHIV had seroprotective titers to at least one serogroup, with individual seroprotection rates of 24%, 28%, and 32% against C, W, and Y, respectively. After a two-dose schedule, vaccine response was 83% for each serogroup, eliciting a vaccine response to all serogroups in 69% of them. One year after vaccination, 75% of CALHIV maintained seroprotective titers against the C serogroup, and 96% against W and Y. None of the HIV-related characteristics analyzed could predict vaccine response or antibody duration.

CONCLUSIONS

CALHIV who received effective TAR and presented a good immuno-virological situation achieved an appropriate vaccine response after two doses of the Men ACWY-TT vaccine, and antibody-mediated protection against serogroups C, W, and Y was maintained in more than 70% of the patients one year after vaccination.

Meningococcal Disease in the Post-COVID-19 Era: A Time to Prepare

The global invasive meningococcal disease (IMD) landscape changed considerably during the COVID-19 pandemic, as evidenced by decreased incidence rates due to COVID-19 mitigation measures, such as limited social contact, physical distancing, mask wearing, and hand washing. Vaccination rates were also lower during the pandemic relative to pre-pandemic levels. Although policymakers may have shifted their focus away from IMD vaccination programs to COVID-19 vaccination programs, strong arguments support implementation and prioritization of IMD vaccination programs; IMD cases have increased in some countries and IMD rates may even have exceeded pre-pandemic levels. Additional concerns include increased susceptibility due to vaccination coverage gaps, increased incidence of other respiratory pathogens, immunity debt from lockdown restrictions, and increased IMD epidemiologic variability. The full range of benefits of widely available and effective meningococcal vaccines needs to be considered, especially in health technology assessments, where the broad benefits of these vaccines are neither accurately quantified nor captured in implementation policy decisions. Importantly, implementation of meningococcal vaccination programs in the current IMD climate also appeals to broader healthcare principles, including preparedness rather than reactive approaches, generally accepted benefit-risk approaches to vaccination, historical precedent, and the World Health Organization's goal of defeating meningitis by 2030. Countries should therefore act swiftly to bolster existing meningococcal vaccination strategies to provide broad coverage across age groups and serogroups given the recent increases in IMD incidence.

Outcomes of adults with invasive meningococcal disease with reduced penicillin susceptibility in Auckland 2004-2017

PURPOSE

The purpose of this study was to assess the clinical outcomes of adults with invasive meningococcal disease (IMD) and to compare the outcomes of patients with IMD caused by a penicillin susceptible isolate (minimum inhibitory concentration (MIC) ≤ 0.06 mg/L) with patients with IMD caused by an isolate with reduced penicillin susceptibility (MIC > 0.06 mg/L). We also assessed the outcomes of patients with IMD caused by an isolate with reduced penicillin susceptibility who were treated exclusively with intravenous (IV) benzylpenicillin.

METHODS

Retrospective study of all culture positive IMD in adult patients (age ≥ 15 years) in the Auckland region from 2004 to 2017.

RESULTS

One hundred and thirty-nine patients were included; 94 had penicillin susceptible isolates (88 cured, 6 died), and 45 had an isolate with reduced penicillin susceptibility (41 cured, 1 possible relapse, 3 died). The median benzylpenicillin/ceftriaxone treatment duration was 3 days for both groups. There was no difference in the patient outcomes of both groups. Eighteen patients with IMD caused by an isolate with reduced penicillin susceptibility received benzylpenicillin alone and were cured.

CONCLUSIONS

This study provides further support to existing data that has shown that short duration IV beta-lactam treatment is effective for IMD in adults. Only a small number of patients with meningitis caused by an isolate with reduced penicillin susceptibility received benzylpenicillin alone, limiting its evaluation. For Neisseria meningitidis meningitis, we recommend ceftriaxone as empiric treatment and as definitive treatment when this is caused by an isolate with reduced penicillin susceptibility.

Neisseria meningitidis serogroup W135 in a traveler visiting Japan from Argentina, 2019

Invasive meningococcal disease (IMD) can occur in travelers returning from mass-gathering events or endemic regions. We present a 60-year-old Argentine traveler to Tokyo who developed IMD by Neisseria meningitidis Serogroup W135 during her stay in Japan. N. meningitidis serogroup W135 infection has become common in Argentina, whereas IMD less commonly occurs in Japan. Considering the prevalence, the patient most likely acquired the infection in Argentina, and it developed in Japan. Air travel enables passengers to reach the four corners of the world within a few days. IMD should be considered in travelers due to its potential to induce rapid clinical deterioration and transmission.

Invasive meningococcal disease in older adults in North America and Europe: is this the time for action? A review of the literature

BACKGROUND

Neisseria meningitidis is an encapsulated Gram-negative diplococcus that asymptomatically colonises the upper respiratory tract in up to 25% of the population (mainly adolescents and young adults). Invasive meningococcal disease (IMD) caused by Neisseria meningitidis imposes a substantial public health burden,. The case fatality rate (CFR) of IMD remains high. IMD epidemiology varies markedly by region and over time, and there appears to be a shift in the epidemiology towards older adults. The objective of our review was to assess the published data on the epidemiology of IMD in older adults (those aged ≥ 55 years)in North America and Europe. Such information would assist decision-makers at national and international levels in developing future public health programmes for managing IMD.

METHODS

A comprehensive literature review was undertaken on 11 August 2020 across three databases: EMBASE, Medline and BIOSIS. Papers were included if they met the following criteria: full paper written in the English language; included patients aged ≥ 56 years; were published between 1/1/2009 11/9/2020 and included patients with either suspected or confirmed IMD or infection with N. meningitidis in North America or Europe. Case studies/reports/series were eligible for inclusion if they included persons in the age range of interest. Animal studies and letters to editors were excluded. In addition, the websites of international and national organisations and societies were also checked for relevant information.

RESULTS

There were 5,364 citations identified in total, of which 76 publications were included in this review. We identified that older adults with IMD were mainly affected by serogroups W and Y, which are generally not the predominant strains in circulation in most countries. Older adults had the highest CFRs, probably linked to underlying comorbidities and more atypical presentations hindering appropriate timely management. In addition, there was some evidence of a shift in the incidence of IMD from younger to older adults.

CONCLUSIONS

The use of meningococcal vaccines that include coverage against serogroups W and Y in immunization programs for older adults needs to be evaluated to inform health authorities' decisions of the relative benefits of vaccination and the utility of expanding national immunization programmes to this age group.

Product review on the IMD serogroup B vaccine Bexsero®

Bexsero® is a multicomponent vaccine composed of four major proteins of Neisseria meningitidis: the fHbp, NHBA, NadA and PorA. This vaccine was licensed against invasive meningococcal disease (IMD) due to serogroup B isolates. When administered alone, Bexsero® showed a safety profile similar to other childhood vaccines. It provides an excellent immunogenicity but that requires booster doses in infants and young children. Although the vaccine does not seem to impact on acquisition of carriage of serogroup B isolates, it confers protection against isolates of serogroup B harboring distinct but cross-reactive variants of fHbp, NadA and NHBA. Primary vaccination schemes in infancy underwent a rapid increase after a toddler booster suggesting an anamnestic response and the establishment of a memory response. As Bexsero® targets sub-capsular proteins that can be conserved regardless the capsule, the vaccine can be effective against non-B isolates such as isolates of serogroups W and X.

Occupational Health Update: Evaluation and Management of Exposures and Postexposure Prophylaxis

Health care personnel (HCP) are at risk of exposure to infectious agents depending on their job duties and other factors. Risks include percutaneous exposure to blood-borne pathogens via sharp injuries (eg, human immunodeficiency virus, hepatitis B virus, hepatitis C virus); exposure by direct contact, droplet, or airborne transmission of pathogens through direct patient care (eg, pertussis, invasive meningococcus infections, tuberculosis); and through indirect contact transmission related to the contaminated health care environment (eg, Clostridioides difficile). Occupational health programs must effectively identify and respond to potential exposures and provide guidance to HCP on postexposure prophylaxis.

Postmarketing surveillance of adverse events following meningococcal B vaccination: data from Apulia Region, 2014-19

Since the multicomponent meningococcal B vaccine introduction, the Apulian Regional Health Authority implemented postmarketing surveillance program, as provided by Italian laws.

From National Pharmacovigilance Network, we selected 4CMenB AEFIs reported in Apulia from 01 January 2014 to 31 December 2019, while the number of 4 cMen B doses administered per year was obtained from the regional immunization database (GIAVA).

For each subject who experienced an adverse event following meningococcal B vaccine (AEFIs), a predefined form was filled in.

A total of 214 AEFIs (26.5 × 100.000 doses) were reported after any dose of MenB-4 c vaccination of which 58/214 (27.1%) were classified as serious (7.2 × 100,000 doses), 145/214 (67.8%) as not serious (180 × 100,000 doses), and 11/214 (5.1%) as undefined (1.3 × 100,000 doses).

The average age of subjects who experimented and AEFI was 30 months. The majority of serious AEFIs were reported in 2- to 11-month-old children (44/57; 77.2%). A total of 31/58 (3.8 × 100,000 doses; 53.4%) serious AEFIs were reported as having a ‘consistent causal association’ with vaccination. Of these, fever/hyperpyrexia was reported in 21/31 (2.6 × 100,000 doses; 67.7%); hypotonic-hyporesponsive episode was reported in 7/31 (0.9 × 100,000 doses [add %-age]) and was the most frequent adverse event with neurological symptoms. A total of 13/31 (41.9%) serious AEFIs classified as ‘consistent causal association’ were reported after the first dose of 4cMenB, of these 5/13 (38.5%) children did not complete the vaccination schedule.

Our data seemed to confirm, in a large population, the a good safety profile of the universal mass vaccination with 4CMENB.

Meningococcal vaccines in China

Meningococcal meningitis caused by Neisseria meningitidis is a reportable infectious disease in China, due to the high incidence of meningitis in the era before the availability of vaccines. The disease incidence was markedly reduced after meningococcal vaccination was introduced in the 1980s. Currently, there are polysaccharide, conjugate, and combined vaccine formulations against meningococcal meningitis in the Chinese market, almost all of which are produced by domestic manufacturers. It is necessary to further enhance national meningococcal surveillance to improve the level of prevention and control of meningococcus. However, the immune efficacy and persistence of immunity of vaccines should be monitored. More importantly, additional investments should be made to develop serogroup B meningococcal vaccines.

Immunization coverage among asplenic patients and strategies to increase vaccination compliance: a systematic review and meta-analysis

BACKGROUND

Asplenic or splenectomized patients have a higher risk (ranging from 10 to 50-fold) than the general population of developing an overwhelming post-splenectomy infection (OPSI). Thus, they should receive specific vaccinations to prevent bacterial infections and influenza. The aim of this meta-analysis was to estimate vaccination coverage (VC) with the recommended vaccines among splenectomized patients; strategies recommended in those studies to improve VC worldwide are considered as well.

RESEARCH DESIGN AND METHODS

Scopus, MEDLINE/PubMed, Google Scholar and ISI Web of Knowledge databases were searched. Research papers, short reports, reviews, and meta-analyses published between January 1, 2010 and July 18, 2020 were included; no geographic restrictions were included. Twenty-four studies were included in the meta-analysis.

RESULTS

For anti-pneumococcal vaccination, coverage was 55.1% (95%CI = 41.0-69.2%), for anti-Hib 48.3% (95%CI = 34.3-52.3%), for anti-meningococcal C/ACYW135 33.7% (95%CI = 23.6-43.9%), for anti-meningococcal B 13.3% (95%CI = 7.0-19.5%) and for anti-influenza 53.2% (95%CI = 22.0-84.4%). Most studies determined a lack of adherence to international guidelines by healthcare workers and suggested the need to better educate health professionals in the management of post-splenectomy patients.

CONCLUSIONS

The meta-analysis showed the suboptimal immunization coverage for the vaccines recommended for asplenic patients. Greater efforts must be made by public health professionals to increase VC in this group of patients at risk. Introducing specific prophylaxis protocols in the clinical routine seems to guarantee better immunization compliance in those patients.

Multiple Linear Regression Model of Meningococcal Disease in Ukraine: 1992-2015

Estimating the rates of invasive meningococcal disease (IMD) from epidemiologic data remains critical for making public health decisions. In Ukraine, such estimations have not been performed. We used epidemiological data to develop a national database. These data were used to estimate the population susceptible to IMD and identify the prevalence of asymptomatic carriers of N. meningitidis using simple epidemiological models of meningococcal disease that may be used by the national policy makers. The goal was to create simple, easily understood analysis of patterns of the infection within Ukraine that would capture the major features of the infection dynamics. Studies used nationally reported data during 1992–2015. A logic model identified the prevalence of carriage and the proportion of the population susceptible to IMD as key drivers of IMD incidence. Multiple linear regression models for all ages (total population) and for children ≤14 years old were fit to national-level data. Linear models with the incidence of IMD as an outcome were highly associated with carriage and estimated susceptible population in both total population and children (R² = 0.994 and R² = 0.978, respectively). The susceptibility rate to IMD in the study total population averaged 0.0034 ± 0.0009% annually. At the national level, IMD can be characterized by the simple interaction between the prevalence of asymptomatic carriage and the proportion of the susceptible population. IMD association with prevalence rates of carriage and the proportion of susceptible population is sufficiently strong for national-level planning of intervention strategies for IMD.

Pharyngeal carriage rates of Neisseria meningitidis in health care professionals at a tertiary university pediatric hospital

Pharyngeal carriage is the reservoir for Neisseria meningitidis in the population and the first step in disease transmission. Especially in young infants and adolescents, N. meningitidis can cause serious invasive infection with high fatality rates and high rates of long-term sequelae among survivors. The aim of this study was to determine N. meningitidis colonization rates in asymptomatic health care professionals at a tertiary university pediatric hospital and to identify risk factors for carriage. This cross-sectional meningococcal carriage survey was conducted between April and October 2018 at the Medical University of Vienna. Individuals working as nurses, pediatricians, or medical students were enrolled. Oropharyngeal swabs were directly plated onto selective agar plates and conventional culture was used for bacterial identification. Meningococcal isolates were further characterized using whole-genome sequencing. A total of 437 oropharyngeal specimens were collected. Overall, meningococcal carriage prevalence was 1.14% (5/437), with 0.7% (3/437) for capsular genotype B, and 0.5% (2/437) for capsular genotype W. Mean age of carriers was significantly lower than of non-carriers (24.2 vs. 35.8; p = 0.004). The highest carriage rate of 4.4% (4/91) was found in the age group 18–25. Carriage was negatively associated with age and timespan working in pediatrics. This is the first study evaluating the prevalence of Neisseria meningitidis carriage in health care professionals working in Pediatrics and Adolescent Medicine. Carriage was in general lower than expected for all age groups, implicating a low risk of meningococcal transmission via this population.

Trajectory of serogroups causing Invasive Meningococcal Disease in Santa Catarina state, Brazil (2007–2019)

The aim of this study was to compare the trajectory of serogroups causing Invasive Meningococcal Disease (IMD) in the Santa Catarina (SC) state with those of whole Brazil. A retrospective analysis of all IMD cases reported from January 2007 to December 2019 was carried out. During the study period, 26,058 IMD cases were registered in Brazil and 644 and in SC state alone. Overall, Brazil showed progressive reduction in cases since 2010, when the meningococcal C conjugate vaccine was introducted on National Immunization Program, while SC showed an increase in total cases since 2013, particularly from serogroups W and C. Serogroups distribution was significantly different between Brazil and SC. The emergence of serogroup W highlights the improved meningococcal surveillance through increased accuracy in identification methods in SC state. This finding is important for discussing recommendations of quadrivalent (ACWY) conjugate vaccines in different geographical areas of Brazil.

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.

The Inflammatory and Hemostatic Response in Sepsis and Meningococcemia

Meningococcemia is notorious for evasion of the host immune system and its rapid progression to fulminant disease, and serves as a unique model for pediatric sepsis. Illness severity is determined by complex interplays among host, pathogen, and environment. The inflammatory host response, including proinflammatory and anti-inflammatory responses in innate and adaptive immunity, skews toward a proinflammatory state. This leads to endothelial dysfunction and activation of the hemostatic response, which may lead to disseminated intravascular coagulation. This article reviews the pathogenesis of sepsis, in particular the inflammatory and hemostatic response in meningococcal sepsis.

A case report of multiple cerebral abscess formation complicating serogroup B Neisseria meningitidis meningitis

Background

Invasive meningococcal disease (IMD) presenting with meningitis causes significant mortality and morbidity. Suppurative complications of serogroup B meningococcal sepsis are rare and necessitate urgent multidisciplinary management to mitigate long-term morbidity or mortality.

Case presentation

We present a rare case of invasive meningococcal disease in a 28-month old boy complicated by multiple abscess formation within a pre-existing antenatal left middle cerebral artery territory infarct. Past history was also notable for cerebral palsy with right hemiplegia, global developmental delay and West syndrome (infantile spasms). Two craniotomies were performed to achieve source control and prolonged antimicrobial therapy was necessary. The patient was successfully discharged following extensive multidisciplinary rehabilitation.

Conclusions

Longstanding areas of encephalomalacia in the left MCA distribution may have facilitated the development of multiple meningococcal serogroup B abscess cavities in the posterior left frontal, left parietal and left temporal lobes following an initial period of cerebritis and meningitis. A combination of chronic cerebral hypoperfusion and some degree of pre-existing necrosis in these areas, may also have facilitated growth of Neisseria meningitidis, leading ultimately to extensive cerebral abscess formation following haematogenous seeding during meningococcemia. In this case report we review similar cases of cerebral abscess or subdural empyema complicating serogroup B meningococcal meningitis.

MenACWY-CRM conjugate vaccine booster dose given 4-6 years after priming: Results from a phase IIIb, multicenter, open label study in adolescents and adults

BACKGROUND

Vaccination strategies against bacterial meningitis vary across countries. In the United States, a single dose of quadrivalent meningococcal conjugate vaccine (MenACWY) is recommended at 11-12 years of age, with a booster dose approximately 5 years later. We assessed immune responses to a booster dose of MenACWY-CRM vaccine after priming with MenACWY-CRM or MenACWY-D vaccines in adolescents and adults.

METHODS

In this phase IIIb, multicenter, open-label study, healthy 15-55-year-olds, who received MenACWY-CRM (N = 301) or MenACWY-D (N = 300) 4-6 years earlier or were meningococcal vaccine-naïve (N = 100), received one MenACWY-CRM vaccine dose. Immunogenicity was evaluated pre-vaccination, 3 or 5 days post-vaccination (sampling subgroups), and 28 days post-vaccination by serum bactericidal activity assay using human complement (hSBA). After vaccination, participants were monitored for 7 days for reactogenicity, 29 days for unsolicited adverse events (AEs), and 181 days for serious AEs and medically-attended AEs.

RESULTS

Sufficiency of the immune response to a MenACWY-CRM booster dose was demonstrated; the lower limit of the 1-sided 97.5% confidence interval for percentages of participants with hSBA seroresponse at 28 days post-vaccination was >75% for each serogroup in those primed with either the MenACWY-CRM or MenACWY-D vaccine. Seroresponse was observed in ≥93.24% of primed participants and ≥35.87% of naïve participants 28 days post-vaccination. At 5 days post-booster, among primed participants, hSBA titers ≥1:8 were achieved in ≥47.14% of participants for MenA and in ≥85.52% of participants for MenC, MenW and MenY, and 3.25- to 8.59-fold increases in hSBA geometric mean titers against each vaccine serogroup were observed. No safety concerns were raised throughout the 6-month follow-up period.

CONCLUSIONS

A booster dose of the MenACWY-CRM vaccine induced a robust and rapid anamnestic response in adolescents and adults, irrespectively of either MenACWY-CRM or MenACWY-D vaccine administered 4-6 years earlier, with an acceptable clinical safety profile. ClinicalTrials.gov registration: NCT02986854.

Epidemiologic Trends, Global Shifts in Meningococcal Vaccination Guidelines, and Data Supporting the Use of MenACWY-TT Vaccine: A Review

Neisseria meningitidis is a major cause of meningitis and septicemia with cases, outbreaks, and epidemics reported globally in industrialized and non-industrialized countries. N. meningitidis is categorized into 12 serogroups; however, only 5 serogroups (A, B, C, W, Y) are responsible for the majority of disease. Invasive meningococcal disease (IMD) occurs unpredictably; protection is therefore best achieved by initiating proactive vaccination strategies. Vaccines are currently available for the five main disease-causing serogroups. With the evolution of meningococcal vaccines and changes in IMD epidemiology, different vaccination strategies have been used. Recently, the rapid clonal expansion of meningococcal serogroup W (MenW) has been associated with a change in the national and regional vaccination recommendations from monovalent meningococcal serogroup C vaccines to meningococcal serogroup A, C, W, Y (MenACWY) vaccines in several countries. This review highlights these and other changes in IMD epidemiology and meningococcal vaccination recommendations, summarizes information available for currently available conjugate MenACWY vaccines, and focuses on clinical study data for the most recently approved MenACWY conjugate vaccine, MenACWY vaccine conjugated to tetanus toxoid (MenACWY-TT). MenACWY-TT studies spanned multiple age groups and generally demonstrated safety and immunogenicity in comparison with other meningococcal vaccines and under concomitant administration of other routine vaccines. Continuous updates to meningococcal vaccine recommendations in response to changing epidemiology, as have been undertaken for MenW, are necessary to ensure optimal population protection. FUNDING: Pfizer, Inc.

One-year antibody persistence and safety of a 4-dose schedule of MenACWY-CRM in healthy infants from South Korea

Purpose

Results from a post-marketing study to generate evidence on 1-year antibody persistence and safety following vaccination of infants from South Korea with the quadrivalent meningococcal conjugate vaccine MenACWY-CRM.

Materials and Methods

In this phase IV, open-label, multi-center study (NCT02446691), 128 infants received MenACWY-CRM at ages 2, 4, 6, and 12 months. One-year antibody persistence following the full vaccination course was evaluated (primary objective) for the four meningococcal serogroups (Men) by serum bactericidal activity assay using human or rabbit complement (hSBA/rSBA). Immune responses at 1-month post-vaccination and safety were also assessed.

Results

The percentage of children with hSBA titers ≥8 ranged between 94% (MenA) and 100% (MenY/W) 1-month post-vaccination, and from 39% (MenA) to 89% (MenY) 1-year post-vaccination. At least 99% and 92% of children had rSBA titers ≥8 and ≥128 against each meningococcal serogroup, 1-month post-vaccination. One-year post-vaccination, the percentage of children with rSBA titers ≥8 and ≥128 ranged from 54% (MenC) to 99% (MenA) and from 30% (MenC) to 98% (MenA). Geometric mean titers declined from 1-month to 1-year post-vaccination, when they varied between 6.8 (MenA) and 53.6 (MenW) by hSBA and between 17.2 (MenC) and 2,269.5 (MenA) by rSBA. At least one solicited and unsolicited adverse event was reported for 79% and 66% of children. Of 36 serious adverse events reported, none were vaccination-related.

Conclusion

Antibody persistence (hSBA/rSBA titers ≥8) was determined in 39%-99% of children 1 year after a 4-dose MenACWY-CRM series during infancy, with an acceptable clinical safety profile.

Impact of pre-hospital antibiotic therapy on mortality in invasive meningococcal disease: a propensity score study

The role of pre-hospital antibiotic therapy in invasive meningococcal diseases remains unclear with contradictory data. The aim was to determine this role in the outcome of invasive meningococcal disease. Observational cohort study of patients with/without pre-hospital antibiotic therapy in invasive meningococcal disease attended at the Hospital Universitari de Bellvitge (Barcelona) during the period 1977-2013. Univariate and multivariate analyses of mortality, corrected by propensity score used as a covariate to adjust for potential confounding, were performed. Patients with pre-hospital antibiotic therapy were also analyzed according to whether they had received oral (group A) or parenteral antibiotics (early therapy) (group B). Five hundred twenty-seven cases of invasive meningococcal disease were recorded and 125 (24%) of them received pre-hospital antibiotic therapy. Shock and age were the risk factors independently related to mortality. Mortality differed between patients with/without pre-hospital antibiotic therapy (0.8% vs. 8%, p = 0.003). Pre-hospital antibiotic therapy seemed to be a protective factor in the multivariate analysis of mortality (p = 0.038; OR, 0.188; 95% CI, 0.013-0.882). However, it was no longer protective when the propensity score was included in the analysis (p = 0.103; OR, 0.173; 95% CI, 0.021-1.423). Analysis of the oral and parenteral pre-hospital antibiotic groups revealed that there were no deaths in early therapy group. Patients able to receive oral antibiotics had less severe symptoms than those who did not receive pre-hospital antibiotics. Age and shock were the factors independently related to mortality. Early parenteral therapy was not associated with death. Oral antibiotic therapy in patients able to take it was associated with a beneficial effect in the prognosis of invasive meningococcal disease.

Evaluation of strain coverage of the multicomponent meningococcal serogroup B vaccine (4CMenB) administered in infants according to different immunisation schedules

The 4-component vaccine 4CMenB, developed against invasive disease caused by meningococcal serogroup B, is approved for use in infants in several countries worldwide. 4CMenB is mostly used as 3 + 1 schedule, except for the UK, where a 2 + 1 schedule is used, and where the vaccine showed an effectiveness of 82.9%. Here we compared the coverage of two 4CMenB vaccination schedules (3 + 1 [2.5, 3.5, 5, 11 months] versus 2 + 1 [3.5, 5, 11 months of age]) against 40 serogroup B strains, representative of epidemiologically-relevant isolates circulating in England and Wales in 2007–2008, using sera from a previous phase 3b clinical trial. The strains were tested using hSBA on pooled sera of infants, collected at one month post-primary and booster vaccination. 4CMenB coverage was defined as the percentage of strains with positive killing (hSBA titres ≥ 4 after immunisation and negative baseline hSBA titres < 2). Coverage of 4CMenB was 40.0% (95% confidence interval [CI]: 24.9–56.7) and 87.5% (95%CI: 73.2–95.8) at one month post-primary and booster vaccination, respectively, regardless of immunisation schedule. Using a more conservative threshold (post-immunisation hSBA titres ≥ 8; baseline ≤ 2), at one month post-booster dose, strain coverages were 80% (3 + 1) and 70% (2 + 1). We used a linear regression model to assess correlation between post-immunisation hSBA data for each strain in the two groups; Pearson’s correlation coefficients were 0.93 and 0.99 at one month post-primary and booster vaccination. Overall, there is no evidence for a difference in strain coverage when 4CMenB is administered according to a 3 + 1 or 2 + 1 infant vaccination schedule.

Epidemiology of Meningitis in Oman-Implications for Future Surveillance

OBJECTIVES

This study aimed to understand the epidemiology of meningitis cases admitted to hospitals in Oman and to identify any changing microbial patterns from the introduction of the new vaccines.

METHODS

A retrospective analysis of all cases of meningitis reported through a national surveillance system. Meningitis is a notifiable disease.

RESULTS

Of a total of 581 cases of meningitis from the period between January 1, 2005 and December 31, 2013, 15% (88) were confirmed to be bacterial in origin and 7.2% (42/581) viral. In 50.9% (296) of patients with suspected pyogenic meningitis, no specific bacterial pathogen were identified, and in 26% of cases (151) a cerebrospinal fluid study could not be undertaken. Among 88 cases with confirmed bacterial pathogens the organisms identified were Streptococcus pneumoniae (65.9%), Neisseria meningitides (18.2%), Haemophilus influenzae (6.8%), and other organisms (9.1%). The peak incidence was in children <2 years of age (39.4%). It showed notable decline in H. influenzae cases as well as pneumococcal meningitis cases, possibly indicative of the successful immunization program.

CONCLUSION

A drop in H. Influenzae and pneumococcal meningitis cases was possibly the effect of the introduction of vaccines. It shows the need for improving diagnostic accuracy, laboratory capacities, and quality of surveillance reporting.

Emergence and spread of resistant N. meningitidis implicated in invasive meningococcal diseases during the past decade (2008-2017)

Neisseria meningitidis is one of the most crucial causes of bacterial meningitis worldwide. The incidence of meningitis due to N. meningitidis greatly changes from one geographical area to the other: 500,000-1,200,000 invasive meningococcal diseases occur each year, with 50,000-135,000 deaths. Once the diagnosis of bacterial meningitis is made, parenteral antibiotic treatment is started as soon as possible. A preventive treatment can also be proposed for those subjects at risk of exposure. Globally, resistance to antibiotics used in the treatment of prophylaxis of meningococcal disease is relatively rare. Penicillin is becoming less useful in the treatment of invasive meningococcal diseases because meningococcal isolates are increasingly less susceptible to this antibiotic. Meningococcal strains less susceptible to ceftriaxone or ciprofloxacin are rare. In addition, resistance to rifampicin is not a current concern as resistant isolates are rarely reported. In conclusion, the emergence of new meningococcal strains with decreasing susceptibility during the last decade should not be ignored, as this could be a worrying phenomenon in the future and justifies a judicious epidemiological survey on a continuous basis.

Meningococcal Pneumonia in a Young Healthy Male

A 23-year-old male presented to the emergency department with one-day history of right-sided pleuritic chest pain, haemoptysis, and fever. In the emergency department, the blood pressure was 140/60 mmHg, heart rate 89/min, body temperature 40°C, respiratory rates 20 breaths/min, and oxygen saturation 98% in room air. Physical examination revealed rales and bronchial breathing in the right infrascapular region. Laboratory analysis showed raised white blood cell counts and elevated inflammation markers. Chest X-ray showed right lower lobe consolidation. Intravenous(IV) ceftriaxone and doxycycline were started for the management of community-acquired pneumonia as per the local guideline. Later, on admission, blood culture was positive for Neisseria meningitidis (N. meningitidis). Ceftriaxone was continued for 4 days, and the patient was discharged while being on oral amoxicillin (1 gm TDS) for another 3 days. He remained well during the outpatient follow-up.

Vaccination strategies for the prevention of meningococcal disease

Routine prophylactic vaccination and mass vaccination strategies have been used to control both endemic and epidemic disease caused by Neisseria meningitidis globally. This review discusses real-world examples of these vaccination strategies, their implementation, and outcomes of these efforts, with the overall goal of providing insights on how to achieve optimal control of meningococcal disease through vaccination in varied settings. Tailoring immunization programs to fit the needs of the target population has the potential to optimally reduce disease incidence.

Immune Responses to Booster Vaccination With Meningococcal ABCWY Vaccine After Primary Vaccination With Either Investigational or Licensed Vaccines: A Phase 2 Randomized Study

BACKGROUND

Current meningococcal prime-boost vaccination schedules include separate vaccines for serogroups ACWY and B. An investigational combined serogroups ABCWY vaccine (MenABCWY) was developed to protect against clinically important Neisseria meningitidis serogroups.

METHODS

In this phase 2, randomized, observer-blind, extension study (NCT01272180), participants 10-25 years of age received 1 booster dose of MenABCWY vaccine at 24 months (M) postprimary series of MenABCWY (2 doses), 4CMenB (2 doses) or MenACWY-CRM vaccine (1 dose). Immune responses to booster dose (1M postbooster) and antibody persistence (24M, 36M postprimary series) were assessed using bactericidal assay with human complement (hSBA). Reactogenicity and safety were evaluated.

RESULTS

One hundred ninety participants were vaccinated. At 1M after the MenABCWY booster dose, seroresponse rates against serogroups ACWY ranged between 85% and 96%, 73% and 100% and 83% and 95% for participants previously receiving MenABCWY, 4CMenB and MenACWY-CRM, respectively. At 12M postbooster dose, ≥67% of participants across all groups had hSBA titers ≥8 for serogroups ACWY, except in 4CMenB-primed individuals for serogroup Y (45%). Across MenABCWY and 4CMenB-primed groups, hSBA titers ≥5 across serogroup B test strains were observed in 82%-100% and 29%-100% of participants at 1M and 12M postbooster, respectively. Geometric mean titers against serogroups ACWY increased from pre- to 1M postboosting with MenABCWY and persisted at 12M. The reactogenicity and safety profile of MenABCWY was similar to that of 4CMenB.

CONCLUSIONS

MenABCWY may be suitable for prime-boost schedules against meningococcal disease, including regimens involving a primary series of either 4CMenB or MenACWY-CRM licensed vaccines.

Immunogenicity and safety of the quadrivalent meningococcal ACWY-tetanus toxoid conjugate vaccine (MenACWY-TT) in splenectomized or hyposplenic children and adolescents: Results of a phase III, open, non-randomized study

BACKGROUND

Individuals with functional or anatomic asplenia are at high risk for meningococcal disease. We evaluated the immunogenicity and safety of 1 and 2 doses of the quadrivalent meningococcal serogroups A, C, W, Y tetanus toxoid-conjugate vaccine (MenACWY-TT) in this high-risk population.

METHODS

This phase III, open-label, controlled, non-randomized study (NCT01641042) enrolled 1-17-year-olds with impaired splenic activity (high-risk group) and age-matched healthy controls (control group). We measured immune responses to MenACWY-TT by serum bactericidal activity assays using rabbit (rSBA) and human (hSBA) complement and in terms of antibodies against polysaccharides of the 4 vaccine serogroups. We evaluated vaccine response rates (VRRs) as 4-fold increases from pre-vaccination levels or titers ≥1:32 (rSBA)/≥1:8 (hSBA). We recorded solicited and unsolicited adverse events (AEs) during 4 and 31 days post-vaccination, and serious AEs (SAEs) and new onset of chronic illnesses (NOCIs) throughout the study.

RESULTS

The according-to-protocol cohort for immunogenicity included 40 participants per group. In both groups, the first MenACWY-TT dose induced rSBA VRRs of 92.5-100% and hSBA VRRs of 55.6-77.1% across vaccine serogroups. Following the second MenACWY-TT dose, all participants had high responses, with rSBA and hSBA VRRs of 73.0-100% across vaccine serogroups. rSBA and hSBA geometric mean titers for each serogroup increased in both groups (with different magnitudes, but ≥13.1-fold) compared with baseline levels. Polysaccharide antibody concentrations ≥2.0 μg/ml were detected in ≥84.4% of participants and were similar between groups. Incidences of solicited and unsolicited AEs were comparable between groups. We recorded SAEs in 4/43 participants in the high-risk group and 1/43 participants in the control group (none vaccine-related). No NOCIs were reported.

CONCLUSION

In this descriptive study, MenACWY-TT induced similar functional and humoral immune responses and had a clinically acceptable safety profile in children and adolescents with impaired splenic activity and in healthy controls.

Meningococcal disease, a clinical and epidemiological review

Meningococcal disease is the acute infection caused by Neisseria meningitidis, which has humans as the only natural host. The disease is widespread around the globe and is known for its epidemical potential and high rates of lethality and morbidity. The highest number of cases of the disease is registered in the semi-arid regions of sub-Saharan Africa. In Brazil, it is endemic with occasional outbreaks, epidemics and sporadic cases occurring throughout the year, especially in the winter. The major epidemics of the disease occurred in Brazil in the 70's caused by serogroups A and C. Serogroups B, C and Y represent the majority of cases in Europe, the Americas and Australia. However, there has been a growing increase in serogroup W in some areas. The pathogen transmission happens for respiratory route (droplets) and clinically can lead to meningitis and sepsis (meningococcemia). The treatment is made with antimicrobial and supportive care. For successful prevention, we have some measures like vaccination, chemoprophylaxis and droplets' precautions. In this review, we have described and clarify clinical features of the disease caused by N. meningitidis regarding its relevance for healthcare professionals.

Invasive meningococcal disease: Impact of short course therapy. A DOOR/RADAR study

BACKGROUND

Invasive meningococcal disease is a severe infection. The appropriate duration of antibiotic therapy is not well established.

METHODS

Two hundred and sixty-three consecutive patients with invasive meningococcal disease treated with 4 days' antibiotic therapy were compared with 264 consecutive patients treated previously at the same center with 7 days' antibiotic therapy. A Desirability of Outcome Ranking (DOOR) and Response Adjusted for Duration of Antibiotic Risk (RADAR) study was also performed.

RESULTS

No relapses were recorded in any patient. Patients on the 4-day course were 63% female, with a median age of 23 years old (IQR 16-54) and patients on the 7-day course were 61% female, with a median age of 17 years old (IQR 12-43). Case fatality rate was 7% in the 4-d patients and 6% in the 7-d patients (p = 0.582). Neurological sequelae were recorded in 6% of the 4-d group and in 7% of the 7-d group ((p = 0.509) and cutaneous sequelae in 3% in both groups. There were no statistical significant differences between the groups in terms of clinical characteristics, laboratory findings or complications. The probability that a patient had a randomly chosen DOOR better with the 4-day regimen than with the 7-day regimen was 80.4% [95% CI 80.1-80.7%].

CONCLUSION

Invasive meningococcal disease may be successfully treated with a four-day course of antibiotic therapy without relapses.

Discordant Effects of Licensed Meningococcal Serogroup B Vaccination on Invasive Disease and Nasal Colonization in a Humanized Mouse Model

Background

The multicomponent meningococcal serogroup B vaccine (4CMenB) is an outer membrane vesicle and recombinant protein-based vaccine licensed to protect against serogroup B meningococcal disease. It remains unknown whether this vaccine will prevent carriage or transmission, key aspects in long-term vaccine success and disease eradication.

Methods

Using a "humanized" transgenic mouse model of nasal colonization, we took a systematic approach to estimate the potential for carriage prevention against antigenically diverse Neisseria meningitidis strains and to compare this protection to an invasive meningococcal disease challenge model.

Results

The 4CMenB vaccine prevented morbidity and mortality after lethal invasive doses of all meningococcal strains tested. Immunization effectively prevented carriage with only 1 of 4 single antigen-matched strains but reduced or prevented nasal colonization by all 4 isolates with multiple cross-reacting antigens. Each immunized mouse had substantial immunoglobulin G targeting the challenge strains, indicating that antibody correlates with protection against sepsis but not nasal carriage.

Conclusions

Immunization with the 4CMenB vaccine elicits a robust humoral response that correlates with protection against invasive challenge but not with prevention of asymptomatic colonization. This suggests that widespread use of this vaccine will reduce morbidity and mortality rates in immunized individuals, with the potential to contribute to herd protection against a subset of strains.

Meningococcal serogroup B vaccine: Knowledge and acceptability among parents in Italy

This study aimed to evaluate the knowledge and attitudes about Meningococcal meningitis B and the relative vaccine for children among a sample of parents in Italy. A cross-sectional investigation was conducted from October to December 2015 among a sample of 910 parents in the geographic area of Naples and Salerno (Italy). In total, 543 of 910 parents returned a completed questionnaire for a response rate of 59.7%. Almost all parents had heard about meningitis (95.8%), 79.8% of these knew the mode of transmission (through respiratory droplets) and 62.5% knew the susceptible population (infants, children and adolescents). Moreover, a large percentage (86%) knew that the vaccine is a preventive measure. Parents who were married, those who had one child, those who did not have information about the MenB vaccine by physicians and those who needed additional information about the MenB vaccine were more likely to know the vaccine as a preventive measure of meningitis. Regarding attitudes toward the MenB vaccine, approximately two thirds of parents considered the vaccine useful (67.2%) and said that they would vaccinate their children (64.1%). Parents who had administered at least one recommended vaccination to their children, those who considered the vaccine useful, those with need for additional information about the vaccine and those who knew that the vaccine was a preventive measure of meningitis were more likely to have a positive attitude to vaccinating their children. Considering the results of our study, it looks appropriate that the knowledge of the population about meningitis and its related vaccinations is improved through correct health education and effective vaccine strategies that are implemented by policy makers.

Targeting the Mucosal Barrier: How Pathogens Modulate the Cellular Polarity Network

The mucosal barrier is composed of polarized epithelial cells with distinct apical and basolateral surfaces separated by tight junctions and serves as both a physical and immunological barrier to incoming pathogens. Specialized polarity proteins are critical for establishment and maintenance of polarity. Many human pathogens have evolved virulence mechanisms that target the polarity network to enhance binding, create replication niches, move through the barrier by transcytosis, or bypass the barrier by disrupting cell-cell junctions. This review summarizes recent advances and compares and contrasts how three important human pathogens that colonize mucosal surfaces, Pseudomonas aeruginosa, Helicobacter pylori, and Neisseria meningitidis, subvert the host cell polarization machinery during infection.

Endogenous Meningococcal Endophthalmitis with Isolated Joint Involvement in Immunocompetent Adults

PURPOSE

We report two cases of endogenous meningococcal endophthalmitis in immunocompetent adults presenting with unilateral ocular disease and joint involvement.

METHODS

A retrospective review of two patients with endogenous endophthalmitis due to Neisseria meningitidis with associated arthropathy was conducted. The clinical presentation, investigations, treatment, and outcomes are presented.

RESULTS

Vitreous sampling confirmed Neisseria meningitidis via polymerase chain reaction (PCR) in both cases. PCR was positive from the knee aspirate of our second case. Both patients received topical steroids and topical, intravitreal and intravenous antibiotics. Despite this, visual outcomes were poor.

CONCLUSIONS

This atypical combination of endogenous meningococcal endophthalmitis associated with meningococcal joint involvement could represent a novel pattern for the presentation of metastatic meningococcal endophthalmitis not previously described. We suggest joint aspirate PCR could be a useful adjunctive test to identify potential causative organisms in such cases where there is concurrent joint involvement in the absence of systemic features.

Adenoid bacterial colonization in a paediatric population

Adenoids play a key role in both respiratory and ear infection in children. It has also been shown that adenoidectomy improves these symptoms in this population. The main goal of the present study was to evaluate adenoid bacterial colonization and document a possible relation with infectious respiratory disease. A prospective observational study was designed to evaluate the proposed hypothesis in a paediatric population submitted to adenoidectomy by either infectious or non-infectious indications and compare these two cohorts. A total of 62 patients with ages ranging from 1 to 12 years old were enrolled in the study. Adenoid surface, adenoid core and middle meatus microbiota were compared. A close association between adenoid colonization and nasal infection was found, supporting that adenoids may function as bacterial reservoir for upper airway infection. The obtained results also contribute to explain the success of adenoidectomy in patients with infectious indications.

Occupational Health Update: Focus on Preventing the Acquisition of Infections with Pre-exposure Prophylaxis and Postexposure Prophylaxis

Health care personnel are commonly exposed to infectious agents via sharp injuries (eg, human immunodeficiency virus, hepatitis B virus, and hepatitis C virus), direct patient care (eg, pertussis and meningococcus), and the contaminated environment (eg, Clostridium difficile). An effective occupational program is a key aspect of preventing acquisition of an infection by offering the following: (1) education of health care personnel regarding proper handling of sharps, early identification and isolation of potentially infectious patients, and hand hygiene; (2) assuring immunity to vaccine-preventable diseases; and, (3) immediate availability of a medical evaluation after a nonprotected exposure to an infectious disease.

Treatment of Meningococcal Disease

Meningococcal disease is a life-threatening infection that may progress rapidly, even after appropriate treatment has commenced. Early suspicion of the diagnosis is vital so that parenteral antibiotic treatment can be administered as soon as possible to reduce the complications of infection. The outcome of meningococcal disease is critically dependent on prompt recognition of two important complications: shock and raised intracranial pressure. Rapid recognition of disease and of these complications, together with appropriate management is crucial to the outcome of affected patients. This article summarizes the clinical features of invasive meningococcal disease, diagnostic tools, treatment modalities, and common post-infection sequelae.

Meningococcal B vaccination: real-world experience and future perspectives

Invasive meningococcal disease (IMD) represents a severe risk for health. It can be considered the most dangerous vaccine-preventable disease due to the high probability of related permanent sequelae and death. The introduction in many countries of the conjugate vaccines against A, C, W135, and Y meningococcal serogroups influenced significantly the impact of the disease. Recently, the difficulties in obtaining an effective vaccine against meningococcal serogroup B (MenB) have been get over through the reverse vaccinology, enabling the recognition of some antigens providing a response against most of circulating MenB strains worldwide. The new 4cMenB vaccine is recommended in Europe, Canada, Australia, the USA, and some Latin American countries. Even if sound data on efficacy and safety profile are available, the results in terms of effectiveness are still limited. The management of the MenB outbreaks in two US universities demonstrated the ability to quickly achieve high vaccination coverage rates and no new cases among immunized subjects were assessed. It is desirable that the opportunity to complete preventive intervention against IMD offered by the new 4cMenB vaccine should be recognized and that this vaccine is included in the vaccination schedule to complete the panel of immunization against Neisseria meningitidis.

Meningococcal quadrivalent tetanus toxoid conjugate vaccine (MenACWY-TT, Nimenrix™): A review of its immunogenicity, safety, co-administration, and antibody persistence

INTRODUCTION

Meningococcal disease is a major cause of morbidity and mortality worldwide with reported epidemics and outbreaks in different parts of the world. Despite the availability of antimicrobial therapy, challenges remain in early recognition and prevention of disease. Several vaccines have been developed to date aiming at preventing disease spread.

DISCUSSION

MenACWY-TT (Nimenrix™) has been extensively studied for use in different age groups. Phase II and III randomized trials have demonstrated its immunogenicity when administered in children aged 1 year and older, adolescents and adults. It has an acceptable safety profile with minor adverse events comparable to other vaccines. Follow up studies have shown persistence of protective antibodies up to three years. MenACWY-TT was safely and effectively co-administered with different recommended vaccines.

CONCLUSION

MenACWY-TT is a safe and immunogenic vaccine that can be used to protect against these four serogroups in individuals older than 1 year of age.

Comparison of Phenotypic and Genotypic Approaches to Capsule Typing of Neisseria meningitidis by Use of Invasive and Carriage Isolate Collections

Neisseria meningitidis serogroup B (MnB) is a leading cause of bacterial meningitis; however, MnB is most commonly associated with asymptomatic carriage in the nasopharyngeal cavity, as opposed to the disease state. Two vaccines are now licensed for the prevention of MnB disease; a possible additional benefit of these vaccines could be to protect against disease indirectly by disrupting nasopharyngeal carriage (e.g., herd protection). To investigate this possibility, accurate diagnostic approaches to characterize MnB carriage isolates are required. In contrast to invasive meningococcal disease (IMD) isolates, which can be readily serogrouped, carriage isolates often lack capsule expression, making standard phenotypic assays unsuitable for strain characterization. Several antibody-based methods were evaluated for their abilities to serogroup isolates and were compared with two genotyping methods (real-time PCR [rt-PCR] and whole-genome sequencing [WGS]) to identify which approach would most accurately ascertain the polysaccharide groups associated with carriage isolates. WGS and rt-PCR were in agreement for 99% of IMD isolates, including those with coding sequences for MnB, MnC, MnW, and MnY, and the phenotypic methods correctly identified serogroups for 69 to 98% of IMD isolates. In contrast, only 47% of carriage isolates were groupable by genotypic methods, due to mutations within the capsule operon; of the isolates identified by genotypic methods, ≤43% were serogroupable with any of the phenotypic methods tested. These observations highlight the difficulties in the serogrouping and capsular genogrouping of meningococcal carriage isolates. Based on our findings, WGS is the most suitable approach for the characterization of meningococcal carriage isolates.

Host-pathogen interaction during bacterial vaccination

Vaccines have been developed and deployed against several important bacterial pathogens of humans, including Neisseria meningitidis, Bordetella pertussis, Streptococcus pneumoniae and Mycobacterium tuberculosis. These vaccines are generally considered a successful public health measure and are effective at controlling disease symptoms and/or burden. However, a troubling consequence of recent vaccination programs has been the selection of vaccine escape mutants, whereby the pathogen displays a different repertoire of immune targets than those represented in the vaccine formulation. To address these issues of antigenic variation and bacterial evolution, continued and sustained efforts in epidemiological surveillance, vaccine development/formulation research, and understanding of the host-pathogen interaction are required.