A randomized trial to determine the tolerability and immunogenicity of a quadrivalent meningococcal glycoconjugate vaccine in healthy adolescents

Meningococcal Vaccination in the United States: Past, Present, And Future

Meningococcal disease is rare but serious, often striking previously healthy adolescents or young adults, with substantial morbidity and mortality. The incidence of meningococcal disease in the USA declined even prior to the issuance of routine recommendations for vaccination, although an uptick in incidence has occurred since 2022. Routine recommendations for adolescent MenACWY vaccination were issued in 2005, and recommendations for adolescent MenB vaccination based on shared clinical decision-making (SCDM) were issued in 2015. Although meningococcal vaccines are safe and effective, their limited duration of protection coupled with low disease incidence result in a high cost per case averted by vaccination, most notably with MenB vaccines. The low cost-effectiveness raises ethical concerns about resource use and the role of economic analyses in policy decisions. However, the potential for substantial public health impact remains. Outer membrane vesicle (OMV)-containing MenB vaccines provide some protection against gonorrhea infections. The recent development of pentavalent ABCWY vaccines provide the opportunity to reduce the number of injections and simplify implementation, provided MenACWY and MenB vaccine schedules are harmonized. Vaccine attributes, implementation issues, and resource utilization will be important considerations in optimization of the US adolescent meningococcal vaccination strategy.

Analysis of immunogenicity and purification methods in conjugated polysaccharide vaccines: a new approach in fighting pathogenic bacteria

Carbohydrates are commonly found in conjunction with lipids or proteins, resulting in the formation of glycoconjugates such as glycoproteins, glycolipids, and proteoglycans. These glycoconjugates are essential in various biological activities, including inflammation, cell-cell recognition, bacterial infections, and immune response. Nonetheless, the isolation of naturally occurring glycoconjugates presents challenges due to their typically heterogeneous nature, resulting in variations between batches in structure and function, impeding a comprehensive understanding of their mechanisms of action. Consequently, there is a strong need for the efficient synthesis of artificial glycoconjugates with precisely described compositions and consistent biological properties. The chemical and enzymatic approaches discussed in this paper present numerous research opportunities to develop customised glycoconjugate vaccines.

Aluminium adjuvants versus placebo or no intervention in vaccine randomised clinical trials: a systematic review with meta-analysis and Trial Sequential Analysis

OBJECTIVES

To assess the benefits and harms of aluminium adjuvants versus placebo or no intervention in randomised clinical trials in relation to human vaccine development.

DESIGN

Systematic review with meta-analysis and trial sequential analysis assessing the certainty of evidence with Grading of Recommendations Assessment, Development and Evaluation (GRADE).

DATA SOURCES

We searched CENTRAL, MEDLINE, Embase, LILACS, BIOSIS, Science Citation Index Expanded and Conference Proceedings Citation Index-Science until 29 June 2021, and Chinese databases until September 2021.

ELIGIBILITY CRITERIA

Randomised clinical trials irrespective of type, status and language of publication, with trial participants of any sex, age, ethnicity, diagnosis, comorbidity and country of residence.

DATA EXTRACTION AND SYNTHESIS

Two independent reviewers extracted data and assessed risk of bias with Cochrane's RoB tool 1. Dichotomous data were analysed as risk ratios (RRs) and continuous data as mean differences. We explored both fixed-effect and random-effects models, with 95% CI. Heterogeneity was quantified with I2 statistic. We GRADE assessed the certainty of the evidence.

RESULTS

We included 102 randomised clinical trials (26 457 participants). Aluminium adjuvants versus placebo or no intervention may have no effect on serious adverse events (RR 1.18, 95% CI 0.97 to 1.43; very low certainty) and on all-cause mortality (RR 1.02, 95% CI 0.74 to 1.41; very low certainty). No trial reported on quality of life. Aluminium adjuvants versus placebo or no intervention may increase adverse events (RR 1.13, 95% CI 1.07 to 1.20; very low certainty). We found no or little evidence of a difference between aluminium adjuvants versus placebo or no intervention when assessing serology with geometric mean titres or concentrations or participants' seroprotection.

CONCLUSIONS

Based on evidence at very low certainty, we were unable to identify benefits of aluminium adjuvants, which may be associated with adverse events considered non-serious.

Immunological non-inferiority of a new fully liquid presentation of the MenACWY-CRM vaccine to the licensed vaccine: results from a randomized, controlled, observer-blind study in adolescents and young adults

A fully liquid MenACWY-CRM vaccine presentation has been developed, modifying the meningococcal serogroup A (MenA) component from lyophilized to liquid. The safety and immunogenicity of the liquid presentation at the end of the intended shelf-life (aged for 24 or 30 months) were compared to the licensed lyophilized/liquid presentation. This multicenter, randomized (1:1), observer-blind, phase 2b study (NCT03433482) enrolled adolescents and young adults (age 10-40 years). In part 1, 844 participants received one dose of liquid presentation stored for approximately 24 months or licensed presentation. In part 2, 846 participants received one dose of liquid presentation stored for approximately 30 months or licensed presentation. After storage, the MenA free saccharide (FS) level was approximately 25% and O-acetylation was approximately 45%. The primary objective was to demonstrate non-inferiority of the liquid presentation to licensed presentation, as measured by human serum bactericidal assay (hSBA) geometric mean titers (GMTs) against MenA, 1-month post-vaccination. Immune responses against each vaccine serogroup were similar between groups. Between-group ratios of hSBA GMTs for MenA were 1.21 (part 1) and 1.11 (part 2), with two-sided 95% confidence interval lower limits (0.94 and 0.87, respectively) greater than the prespecified non-inferiority margin (0.5), thus meeting the primary study objective. No safety concerns were identified. Despite reduced O-acetylation of MenA and increased FS content, serogroup-specific immune responses induced by the fully liquid presentation were similar to those induced by the licensed MenACWY-CRM vaccine, with non-inferior anti-MenA responses. The safety profiles of the vaccine presentations were similar.

Meningococcal Vaccination: Recommendations of the Advisory Committee on Immunization Practices, United States, 2020

This report compiles and summarizes all recommendations from CDC's Advisory Committee on Immunization Practices (ACIP) for use of meningococcal vaccines in the United States. As a comprehensive summary and update of previously published recommendations, it replaces all previously published reports and policy notes. This report also contains new recommendations for administration of booster doses of serogroup B meningococcal (MenB) vaccine for persons at increased risk for serogroup B meningococcal disease. These guidelines will be updated as needed on the basis of availability of new data or licensure of new meningococcal vaccines. ACIP recommends routine vaccination with a quadrivalent meningococcal conjugate vaccine (MenACWY) for adolescents aged 11 or 12 years, with a booster dose at age 16 years. ACIP also recommends routine vaccination with MenACWY for persons aged ≥2 months at increased risk for meningococcal disease caused by serogroups A, C, W, or Y, including persons who have persistent complement component deficiencies; persons receiving a complement inhibitor (e.g., eculizumab [Soliris] or ravulizumab [Ultomiris]); persons who have anatomic or functional asplenia; persons with human immunodeficiency virus infection; microbiologists routinely exposed to isolates of Neisseria meningitidis; persons identified to be at increased risk because of a meningococcal disease outbreak caused by serogroups A, C, W, or Y; persons who travel to or live in areas in which meningococcal disease is hyperendemic or epidemic; unvaccinated or incompletely vaccinated first-year college students living in residence halls; and military recruits. ACIP recommends MenACWY booster doses for previously vaccinated persons who become or remain at increased risk.In addition, ACIP recommends routine use of MenB vaccine series among persons aged ≥10 years who are at increased risk for serogroup B meningococcal disease, including persons who have persistent complement component deficiencies; persons receiving a complement inhibitor; persons who have anatomic or functional asplenia; microbiologists who are routinely exposed to isolates of N. meningitidis; and persons identified to be at increased risk because of a meningococcal disease outbreak caused by serogroup B. ACIP recommends MenB booster doses for previously vaccinated persons who become or remain at increased risk. In addition, ACIP recommends a MenB series for adolescents and young adults aged 16-23 years on the basis of shared clinical decision-making to provide short-term protection against disease caused by most strains of serogroup B N. meningitidis.

Immunogenicity and safety of a quadrivalent meningococcal tetanus toxoid-conjugate vaccine (MenACYW-TT) in ≥56-year-olds: A Phase III randomized study

BACKGROUND

Invasive meningococcal disease has a high mortality rate in individuals aged ≥56 years, but no vaccine is currently licensed in the USA for this age group. This study assessed the safety and immunogenicity of an investigational quadrivalent meningococcal tetanus toxoid conjugate vaccine (MenACYW-TT) compared with a meningococcal quadrivalent polysaccharide vaccine (MPSV4) in this age group.

METHODS

This was a Phase III, modified double-blind, randomized, non-inferiority study (NCT02842866) across 35 clinical sites in the USA and Puerto Rico in individuals aged ≥56 years. A single dose of the MenACYW-TT (n = 451) or MPSV4 vaccine (n = 455) was administered on Day 0. A serum bactericidal assay with human (hSBA) and baby rabbit (rSBA) complement was used to measure antibodies against serogroups A, C, W, and Y test strains at baseline and Day 30. Safety data were collected up to six months post-vaccination.

RESULTS

The seroresponse to MenACYW-TT was non-inferior to MPSV4 for each of the serogroups (A: 58.2% vs. 42.5%; C: 77.1% vs. 49.7%; W: 62.6% vs. 44.8%, Y: 74.4% vs. 43.4%, respectively). At Day 30, participants achieving hSBA titers ≥1:8 were higher for all serogroups after MenACYW-TT vs. MPSV4 (77.4-91.7 vs. 63.1-84.2%, respectively). No safety concerns were identified for either vaccine.

CONCLUSION

MenACYW-TT was well-tolerated and immunogenic in ≥56-year-olds, offering the potential to replace MPSV4 in this age group.

Results from a large post-marketing safety surveillance study in the Republic of Korea with a quadrivalent meningococcal CRM-conjugate vaccine in individuals aged 2 months-55 years

The quadrivalent meningococcal conjugate vaccine MenACWY-CRM is approved in the Republic of Korea for use in individuals from 2 months of age. This single-arm, open-label, observational, multicenter, post-marketing study (NCT01766206) assessed the safety of MenACWY-CRM vaccine administered according to local clinical practice. A total of 3939 individuals aged 2 months–55 years provided safety data post-vaccination; the analysis was conducted on the per-protocol set (3920 participants). Solicited and unsolicited adverse events (AEs) were collected over 7 days post-vaccination and medically-attended AEs (MAAEs) and serious AEs (SAEs) over 29 days post-vaccination. Among recorded solicited AEs, injection site AEs were reported by 21.38% of participants, with tenderness/pain being most frequent across age groups; systemic AEs were reported in 13.95% of participants, with irritability (in ˂6-year-olds), headache and myalgia (in ≥6 year-olds) being the most frequently reported. Most solicited AEs were mild or moderate in nature. The percentage of participants reporting unsolicited AEs varied in the study population, i.e. 12.56% in participants aged 2–23 months and 3.18% in those ≥2 years of age. Overall, less than 22% of unsolicited AEs were considered as related to vaccination. MAAEs (10.89% of participants) were mostly mild; 2.82% were considered as related to vaccination. Three (0.46%) and 5 (0.15%) SAEs (none vaccination-related) occurred in participants aged 2–23 months and 2–55 years, respectively. No deaths were reported. The safety profile for MenACWY-CRM in this post-marketing surveillance was consistent with observations from studies conducted during the vaccine’s clinical development, with no new safety concerns.

Persistence and 4-year boosting of the bactericidal response elicited by two- and three-dose schedules of MenB-FHbp: A phase 3 extension study in adolescents

BACKGROUND

The period of heightened risk of invasive meningococcal disease in adolescence extends for >10 years. This study aimed to evaluate persistence of the immune response to the serogroup B meningococcal (MenB) vaccine MenB-FHbp (Trumenba^®, Bivalent rLP2086) under two- and three-dose primary vaccination schedules, both of which are approved in the United States and the European Union, and to assess safety and immunogenicity of a booster dose.

METHODS

This was an open-label extension study of a phase 2 randomized MenB-FHbp study (primary study). This interim analysis includes data through 1 month after booster vaccination. In the primary study, adolescents 11-18 years of age were randomized using an interactive voice or web-based response system to receive 120 μg MenB-FHbp under 0-, 1-, 6-month; 0-, 2-, 6-month; 0-, 6-month; 0-, 2-month; or 0-, 4-month schedules (termed study groups for the current analysis). For the primary study, participants were blinded to their vaccine study group allocation, but investigators and the study sponsor were unblinded. Immune responses in subjects from the primary study were evaluated through 48 months after primary vaccination (persistence stage; 17 sites in Czech Republic, Denmark, Germany, and Sweden). Safety and immunogenicity of a booster dose given at 48 months after primary vaccination (booster stage; 14 sites in Czech Republic, Denmark, and Sweden) were also assessed. Immune responses were evaluated in serum bactericidal assays with human complement (hSBAs) using four MenB test strains representative of disease-causing MenB strains in the United States and Europe and expressing factor H binding proteins (FHbps) heterologous to the vaccine antigens. The primary immunogenicity endpoints were the proportions of subjects with hSBA titers greater than or equal to the assays' lower limit of quantitation (LLOQ; 1:8 or 1:16 depending on strain) at 12, 18, 24, 36, and 48 months after primary vaccination (persistence stage) and 1 and 48 months after the primary vaccination series and 1 month after receipt of the booster dose (booster stage). Safety evaluations during the booster stage included local reactions and systemic events by severity, antipyretic use, adverse events (AEs), immediate AEs, serious AEs (SAEs), medically attended AEs (MAEs), newly diagnosed chronic medical conditions (NDCMCs), and missed days of school and work because of AEs. The modified intent-to-treat (mITT) population was used for immunogenicity evaluations in the persistence stage. The booster stage immunogenicity evaluations used the evaluable immunogenicity population; analyses were also performed in the mITT population. For the persistence stage, safety evaluations included subjects with at least one blood draw, whereas for the booster stage, they included subjects who received the booster dose and had available safety data. This trial is registered at ClinicalTrials.gov number NCT01543087.

FINDINGS

A total of 465 subjects were enrolled in the persistence stage, and 271 subjects were enrolled in the booster stage. Sera for the extension phase of this interim analysis were collected from September 7, 2012 to December 7, 2015. One month after primary vaccination, 73.8-100.0% of subjects depending on study group responded with hSBA titers ≥LLOQ. Response rates declined during the 12 months after last primary vaccination and then remained stable through 48 months, with 18.0-61.3% of subjects depending on study group having hSBA titers ≥LLOQ at this time point. One month after receipt of the booster dose, 91.9-100.0% of subjects depending on study group had hSBA titers ≥LLOQ against the four primary strains individually and 91.8-98.2% had hSBA titers ≥LLOQ against all four strains combined (composite response). Geometric mean titers were higher after booster vaccination than at 1 month after primary vaccination. Immune responses were generally similar across study groups, regardless of whether a two- or three-dose primary series was received. None of the AEs (2.2-6.9% of subjects depending on study group) or NDCMCs (1.8-5.0%) that were reported during the persistence stage were considered related to the investigational product. Local reactions and systemic events were reported by 84.4-93.8% and 68.8-76.6% of subjects depending on study group, respectively, in the booster stage; these were generally similar across study groups, transient, and less frequent than after any primary vaccination. Additionally, there was no general progressive worsening in severity of reactogenicity events (ie, potentiation; ≤3 subjects per group), and reactogenicity events did not lead to any study withdrawals. No NDCMCs or immediate AEs were reported during the booster stage. AEs were reported by 3.7-12.5% of subjects depending on study group during the booster stage. The two possibly related AEs included a mild worsening of psoriasis and a severe influenza-like illness that resolved in 10 days.

INTERPRETATION

Immune responses declined after the primary vaccination series; however, a substantially greater number of subjects retained protective responses at 48 months after primary vaccination compared with subjects having protective responses before vaccination. Persistence trends were similar across all 5 study groups regardless of whether a two- or three-dose primary schedule was received. Furthermore, a booster dose given 48 months after primary vaccination was safe, well-tolerated, and elicited robust immune responses indicative of immunologic memory; these responses were similar between two- and three-dose primary schedule study groups. Use of a booster dose may help further extend protection against MenB disease in adolescents.

FUNDING

Pfizer Inc.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT COMMENTARY

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

Routinely vaccinating adolescents against meningococcus: targeting transmission & disease

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

Factors contributing to the immunogenicity of meningococcal conjugate vaccines

Various glycoprotein conjugate vaccines have been developed for the prevention of invasive meningococcal disease, having significant advantages over pure polysaccharide vaccines. One of the most important features of the conjugate vaccines is the induction of a T-cell dependent immune response, which enables both the induction of immune memory and a booster response after repeated immunization. The nature of the carrier protein to which the polysaccharides are chemically linked, is often regarded as the main component of the vaccine in determining its immunogenicity. However, other factors can have a significant impact on the vaccine's profile. In this review, we explore the physico-chemical properties of meningococcal conjugate vaccines, which can significantly contribute to the vaccine's immunogenicity. We demonstrate that the carrier is not the sole determining factor of the vaccine's profile, but, moreover, that the conjugate vaccine's immunogenicity is the result of multiple physico-chemical structures and characteristics.

Comparative Assessment of a Single Dose and a 2-dose Vaccination Series of a Quadrivalent Meningococcal CRM-conjugate Vaccine (MenACWY-CRM) in Children 2-10 Years of Age

BACKGROUND

We compared the immunogenicity, safety and 1-year antibody persistence of a single-dose and a 2-dose series of a licensed meningococcal ACWY-CRM conjugate vaccine (MenACWY-CRM) in 2- to 10-year-old children.

METHODS

In this phase III, multicenter, observer-blind study, children aged 2-5 years (n = 359) and 6-10 years (n = 356) were randomized 1:1 to receive 2 doses of MenACWY-CRM (ACWY2) or 1 dose of placebo followed by 1 dose of MenACWY-CRM (ACWY1), 2 months apart. Immunogenicity was measured using serum bactericidal activity with human complement (hSBA). Primary outcomes were to assess the immunologic noninferiority and superiority of ACWY2 versus ACWY1.

RESULTS

One-month after the second dose, the hSBA seroresponse in ACWY2 was noninferior to ACWY1 for all 4 serogroups, in both age cohorts, and was superior for serogroups C and Y in the 2- to 5-year-old age cohort and for serogroup Y in the 6- to 10-year-old age cohort. Overall, 90%-99% of subjects in ACWY2 and 65%-96% in ACWY1 had hSBA titers ≥ 8; geometric mean titers were 1.8- to 6.4-fold higher in ACWY2 than ACWY1 across serogroups. At 1 year postvaccination, geometric mean titers declined, and the differences between ACWY2 and ACWY1 remained significant for serogroups A and C in the 2- to 5-year-old age cohort and for serogroups C and Y in the 6- to 10-year-old age cohort. The safety profile of MenACWY-CRM was similar in both groups.

CONCLUSIONS

The single dose and 2-dose MenACWY-CRM series were immunogenic and well tolerated. Although antibody responses were greater after 2 doses, especially in the 2- to 5-year-old age cohort, this difference was less pronounced at 1 year postvaccination.

Approach to the Discovery, Development, and Evaluation of a Novel Neisseria meningitidis Serogroup B Vaccine

In this chapter, we describe a research and development pathway to identify and demonstrate the efficacy of a Neisseria meningitidis non-capsular vaccine, the recently licensed N. meningitidis serogroup B (MnB) vaccine, Trumenba(®). While other approaches have been followed in the identification of a MnB vaccine (Pizza et al. Science 287:1816-1820, 2000), the methods described here reflect the distinctive approach and experiences in discovering and developing Trumenba(®). In contrast to the development and licensure of polysaccharide-conjugate vaccines against meningococcal serotypes A, C, W, and Y, the development of a vaccine to produce broadly protective antibodies against meningococcal serogroup B has proved difficult, due to the antigenic mimicry of the serogroup B polysaccharide capsule, which is composed of polysialic acid structures similar to those expressed on human neuronal cells. Early development efforts for these vaccines failed because the MnB polysaccharide structures resemble autoantigens and thus were poorly immunogenic. The development of an MnB vaccine has therefore focused on non-polysaccharide approaches. It was critical to identify MnB cell surface-exposed antigens capable of inducing a protective response against diverse, circulating strains of invasive MnB to ensure global coverage. Once candidate antigens were identified, it was important to characterize antigenic variation and expression levels, and subsequently to assure that antigens were expressed broadly among diverse clinical isolates. Prior to the initiation of clinical trials in humans, candidate vaccine antigens were tested in functional immunogenicity assays and yielded responses that were correlated with protection from meningococcal disease. These functional immunogenicity assays (serum bactericidal assays using human complement, hSBAs) measure the titer of complement-dependent bactericidal antibodies in serum from immunized test animals using diverse clinical MnB isolates as targets. Following optimization of vaccine antigenic components based on hSBA responses in preclinical models, animal toxicology tests were performed. Initial clinical studies (Phase 1 and 2) subsequently provided data to support (1) safety and immunogenicity of the vaccine formulation, and (2) the dose and schedule. Phase 3 clinical trials were carried out in the target populations to provide the clinical confirmation of safety and efficacy required for vaccine licensure.

Long-term immunogenicity and safety after a single dose of the quadrivalent meningococcal serogroups A, C, W, and Y tetanus toxoid conjugate vaccine in adolescents and adults: 5-year follow-up of an open, randomized trial

Background

Long-term protection against meningococcal disease is associated with persistence of post-vaccination antibodies at protective levels. We evaluated the bactericidal antibody persistence and safety of the quadrivalent meningococcal serogroups A, C, W and Y tetanus-toxoid conjugate vaccine (MenACWY-TT) and the meningococcal polysaccharide serogroups A, C, W, and Y vaccine (MenACWY-PS) up to 5 years post-vaccination.

Methods

This phase IIb, open, randomized, controlled study conducted in the Philippines and Saudi Arabia consisted of a vaccination phase and a long-term persistence phase. Healthy adolescents and adults aged 11–55 years were randomized (3:1) to receive a single dose of MenACWY-TT (ACWY-TT group) or MenACWY-PS (Men-PS group). Primary and persistence results up to 3 years post-vaccination have been previously reported. Antibody responses against meningococcal serogroups A, C, W, and Y were assessed by a serum bactericidal antibody assay using rabbit complement (rSBA, cut-off titers 1:8 and 1:128) at Year 4 and Year 5 post-vaccination. Vaccine-related serious adverse events (SAEs) and cases of meningococcal disease were assessed up to Year 5.

Results

Of the 500 vaccinated participants, 404 returned for the Year 5 study visit (Total Cohort Year 5). For the Total Cohort Year 5, 71.6–90.0 and 64.9–86.3 % of MenACWY-TT recipients had rSBA titers ≥1:8 and ≥1:128, respectively, compared to 24.8–74.3 and 21.0–68.6 % of MenACWY-PS recipients. The rSBA geometric mean titers (GMTs) remained above the pre-vaccination levels in both treatment groups. Exploratory analyses suggested that both rSBA GMTs as well as the percentages of participants with rSBA titers above the cut-offs were higher in the ACWY-TT than in the Men-PS group for serogroups A, W and Y, with no apparent difference for MenC. No SAEs related to vaccination or cases of meningococcal disease were reported up to Year 5.

Conclusion

These results suggest that a single dose of MenACWY-TT could protect at least 72 % of vaccinated adolescents and adults against meningococcal disease at least 5 years post-vaccination.

Trial registration

ClinicalTrials.gov NCT00356369

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1138-y) contains supplementary material, which is available to authorized users.

Safety and immunogenicity of meningococcal ACWY CRM197-conjugate vaccine in children, adolescents and adults in Russia

Neisseria meningitidis is the leading cause of bacterial invasive infections in people aged <15 years in the Russian Federation. The aim of this phase III, multicenter, open-label study was to assess the immunogenicity and safety of the quadrivalent meningococcal CRM197-conjugate vaccine MenACWY when administered to healthy Russian subjects aged 2 years and above. A total of 197 subjects were immunized with a single dose of the vaccine, and serogroup-specific serum bactericidal activity was measured pre and 1-month post-vaccination with human complement (hSBA) serum titers. Regardless of baseline serostatus, 1 month after a single dose of MenACWY-CRM197 85% (95%CI, 79-90%) of subjects showed serologic response against serogroup A, 74% (67-80%) against serogroup C, 60% (53-67%) against serogroup W, and 83% (77-88%) against serogroup Y. The percentage of subjects with hSBA titers ≥ 1:8 1 month after vaccination was 89% (83-93%) against serogroup A, 84% (78-89%) against serogroup C, 97% (93-99%) against serogroup W, and 88% (82-92%) against serogroup Y. Comparable results were obtained across all subjects: children (2 to 10 years), adolescents (11 to 17 years), and adults (≥18 years). The MenACWY-CRM197 vaccine showed an acceptable safety profile and was well tolerated across all age groups, with no serious adverse events or deaths reported during the study. In conclusion, a single dose of meningococcal MenACWY-CRM197 vaccine is immunogenic and has an acceptable safety profile, provides a broad protection against the most frequent epidemic serogroups, and is a suitable alternative to currently available unconjugated monovalent or bivalent polysaccharide vaccines in Russia.

Immunogenicity and safety of a single dose of a CRM-conjugated meningococcal ACWY vaccine in children and adolescents aged 2-18 years in Taiwan: results of an open label study

BACKGROUND

MenACWY-CRM (Menveo®, Novartis Vaccines, Siena, Italy) is a quadrivalent meningococcal conjugate vaccine developed to help prevent invasive meningococcal disease caused by Neisseria meningitidis serogroups A, C, W, and Y. It is approved within the European Union in persons >2 years of age and in persons from 2 months to 55 years of age in the United States, among other countries. Little is known about the immunogenicity and safety of this vaccine in Taiwanese children >2 years and adolescents. This study assessed the immunogenicity and safety of a single injection of MenACWY-CRM vaccine in Taiwanese subjects aged 2-18 years old.

METHODS

In this phase III, multicentre, open-label study 341 subjects received one dose of MenACWY-CRM. Immunogenicity measures were rates of seroresponse (defined as the proportion of subjects with a postvaccination hSBA ≥1:8 if the prevaccination (baseline) titre was <1:4, or at least a fourfold higher hSBA titre than baseline if the prevaccination titre was ≥1:4), percentages of subjects with serum bactericidal activity (hSBA) ≥1:8 for serogroups A, C, W and Y and hSBA geometric mean titres (GMTs). Local and systemic reactions and all adverse events (AEs) were recorded for 7 days, and medically attended AEs for 1 month post-vaccination.

RESULTS

Seroresponse rates after MenACWY-CRM vaccination at Day 29 for the serogroups A, C, W, and Y were 83%, 93%, 50%, and 65%, respectively. At Day 29 the percentages of subjects with hSBA ≥1:8 against all four serogroups A, C, W and Y were: 83%, 96%, 96% and 82%, respectively. GMTs against all serogroups rose by ≥7-fold from baseline to Day 29. The vaccine was well tolerated.

CONCLUSIONS

A single dose of MenACWY-CRM demonstrated a robust immune response, and an acceptable safety profile in Taiwanese children and adolescents.

Randomized clinical trial to evaluate the immunogenicity of quadrivalent meningococcal conjugate and polysaccharide vaccines in adults in the United kingdom

Meningococcal conjugate vaccines are today successfully deployed in universal programs for children and adolescents in different geographic regions to control meningitis and septicemia. However, in adults, the advantages of these conjugates over the older polysaccharide vaccines are less clear. In this randomized clinical trial, we demonstrated that both conjugate and polysaccharide quadrivalent meningococcal vaccines elicit protective antibody responses in adults aged 18 to 70. (This study has been registered at www.clinicaltrials.gov under registration no. NCT00901940.).

Protein carriers of conjugate vaccines: characteristics, development, and clinical trials

The immunogenicity of polysaccharides as human vaccines was enhanced by coupling to protein carriers. Conjugation transformed the T cell-independent polysaccharide vaccines of the past to T cell-dependent antigenic vaccines that were much more immunogenic and launched a renaissance in vaccinology. This review discusses the conjugate vaccines for prevention of infections caused by Hemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis. Specifically, the characteristics of the proteins used in the construction of the vaccines including CRM, tetanus toxoid, diphtheria toxoid, Neisseria meningitidis outer membrane complex, and Hemophilus influenzae protein D are discussed. The studies that established differences among and key features of conjugate vaccines including immunologic memory induction, reduction of nasopharyngeal colonization and herd immunity, and antibody avidity and avidity maturation are presented. Studies of dose, schedule, response to boosters, of single protein carriers with single and multiple polysaccharides, of multiple protein carriers with multiple polysaccharides and conjugate vaccines administered concurrently with other vaccines are discussed along with undesirable consequences of conjugate vaccines. The clear benefits of conjugate vaccines in improving the protective responses of the immature immune systems of young infants and the senescent immune systems of the elderly have been made clear and opened the way to development of additional vaccines using this technology for future vaccine products.

Meningococcal vaccines: current issues and future strategies

Since the introduction of the first meningococcal conjugate vaccines in 1999, remarkable progress has been made in reducing the morbidity and mortality caused by meningococcal disease. Currently, varying meningococcal conjugate vaccines provide protection against serogroups A, C, Y, and W meningococcal disease. A large impact has been seen after vaccine introduction, particularly in the UK after vaccinating all 1-17 year olds. The introduction of serogroup A conjugate vaccine in the meningitis belt has the potential to control epidemics of disease that disproportionately affect this area of the world. Issues remain that require continued vigilance with disease surveillance and frequent reassessment of vaccine strategies. These issues include duration of protection, potential increases in non-vaccine serogroups, and vaccine safety and potential interference with other routine vaccines. Serogroup B meningococcal vaccines are protein-based vaccines, with the first approved in early 2013. Understanding the potential impact of serogroup B vaccines is critical to developing future meningococcal vaccination strategies.

Mutant Native Outer Membrane Vesicles Combined with a Serogroup A Polysaccharide Conjugate Vaccine for Prevention of Meningococcal Epidemics in Africa

Background

The meningococcal serogroup A (MenA) polysaccharide conjugate vaccine used in Sub-Saharan Africa does not prevent disease caused by MenW or MenX strains, which also cause epidemics in the region. We investigated the vaccine-potential of native outer membrane vesicles with over-expressed factor H-binding protein (NOMV-fHbp), which targeted antigens in African meningococcal strains, and was combined with a MenA polysaccharide conjugate vaccine.

Methodology/Principal Findings

The NOMV-fHbp vaccine was prepared from a mutant African MenW strain with PorA P1.5,2, attenuated endotoxin (ΔLpxL1), deleted capsular genes, and over-expressed fHbp in variant group 1. The NOMV-fHbp was adsorbed with Al(OH)₃ and used to reconstitute a lyophilized MenA conjugate vaccine, which normally is reconstituted with liquid MenC, Y and W conjugates in a meningococcal quadrivalent conjugate vaccine (MCV4-CRM, Novartis). Mice immunized with the NOMV-fHbp vaccine alone developed serum bactericidal (human complement) activity against 13 of 15 African MenA strains tested; 10 of 10 African MenX strains, 7 of 7 African MenW strains, and 6 of 6 genetically diverse MenB strains with fHbp variant group 1 (including 1 strain from The Gambia). The combination NOMV-fHbp/MenA conjugate vaccine elicited high serum bactericidal titers against the two MenA strains tested that were resistant to bactericidal antibodies elicited by the NOMV-fHbp alone; the combination elicited higher titers against the MenA and MenW strains than those elicited by a control MCV4-CRM vaccine (P<0.05); and high titers against MenX and MenB strains. For most strains, the titers elicited by a control NOMV-fHbp knock out vaccine were <1∶10 except when the strain PorA matched the vaccine (titers >1∶000).

Conclusion/Significance

The NOMV-fHbp/MenA conjugate vaccine provided similar or higher coverage against MenA and MenW strains than a quadrivalent meningococcal conjugate vaccine, and extended protection against MenX strains responsible for epidemics in Africa, and MenB strains with fHbp in variant group 1.

Immunogenicity and safety of a meningococcal serogroup A, C, Y and W glycoconjugate vaccine, ACWY-TT

A quadrivalent meningococcal serogroup A, C, W and Y conjugate vaccine (ACWY), utilising tetanus toxoid (TT) as its carrier protein (ACWY-TT; Nimenrix™, GlaxoSmithKline Vaccines, Rixensart, Belgium) has been demonstrated to be safe and immunogenic when administered to young children from 12 months of age, older children, adolescents, and adults. Administration of a single dose of ACWY-TT induces protective serum bactericidal antibodies against all four serogroups as well as good antibody persistence. Coadministration studies have demonstrated that ACWY-TT can be administered with diphtheria, tetanus, three-component acellular pertussis, hepatitis B, inactivated polio virus and Haemophilus influenzae type b conjugate vaccine (DTaP3-IPV-HBV/Hib, Infanrix™ hexa; GlaxoSmithKline Vaccines, Rixensart, Belgium); measles, mumps, rubella, varicella vaccine (Priorix-Tetra™; GlaxoSmithKline Vaccines, Rixensart, Belgium); 10-valent pneumococcal conjugate vaccine (Synflorix(®); GlaxoSmithKline Vaccines, Rixensart, Belgium); hepatitis A and B vaccine (Twinrix(®); GlaxoSmithKline Vaccines, Rixensart, Belgium); and seasonal influenza vaccine (Fluarix™; GlaxoSmithKline Vaccines, Rixensart, Belgium). Studies in young infants from 2 months of age have now commenced but immunisation with a single dose of ACWY-TT from 12 months of age is a safe and immunogenic option in the prevention of meningococcal disease.

Antibody persistence and response to a booster dose of a quadrivalent conjugate vaccine for meningococcal disease in adolescents

BACKGROUND

In a previous randomized phase 2 study in adolescents, a CRM197 meningococcal conjugate vaccine against serogroups A, C, W-135 and Y (MenACWY-CRM) was well tolerated and immunogenic, compared with a plain polysaccharide vaccine (MenACWY-PS).

METHODS

This extension study assessed antibody persistence 5 years after primary vaccination with MenACWY-CRM (n = 50) or MenACWY-PS (n = 51), and the immunogenicity and reactogenicity of a dose of MenACWY-CRM given 5 years after primary vaccination; antibody response was also compared with vaccine-naive controls (n = 54). The primary endpoints were the percentage of subjects with titers ≥8 by serum bactericidal activity assay using human complement (hSBA) 5 years after primary vaccination and hSBA geometric mean titers 1 month after the MenACWY-CRM dose given in the current study.

RESULTS

Five years after primary vaccination, over 70% of subjects who had received MenACWY-CRM were seropositive (hSBA titers ≥8) for serogroups C, W-135 and Y; for serogroups C and Y, the percentages of seropositive subjects were significantly higher in subjects previously vaccinated with MenACWY-CRM than in subjects previously vaccinated with MenACWY-PS. The MenACWY-CRM dose given 5 years postprimary vaccination elicited an anamnestic response across serogroups in those previously vaccinated with MenACWY-CRM. Responses in those previously vaccinated with MenACWY-PS were less robust but adequate and similar to that seen in the vaccine-naive group, both in magnitude and kinetics. MenACWY-CRM was well tolerated in all 3 groups.

CONCLUSION

MenACWY-CRM provided a broad and persistent immune response in adolescents. A subsequent dose of MenACWY-CRM elicited an adequate antibody response, regardless of vaccine history.

Use of MenACWY-CRM in adolescents in the United States

Adolescents constitute a high-risk group for invasive meningococcal disease. MenACWY-CRM (Menveo, Novartis Vaccines, Cambridge, MA) is a quadrivalent meningococcal conjugate vaccine indicated to prevent invasive meningococcal disease caused by Neisseria meningitidis serogroups A, C, W-135, and Y. It has been approved for use in persons age 2-55 years. The tolerability and immunogenicity of MenACWY-CRM in adolescents have been ascertained in phase 2 and 3 trials against MPSV4 (Menomune, sanofi pasteur, Swiftwater, PA), an unconjugated quadrivalent meningococcal vaccine, and MenACWY-D (Menactra, sanofi pasteur), another conjugated quadrivalent meningococcal vaccine. Clinical trials also have demonstrated that MenACWY-CRM is well tolerated and immunogenic when administered to adolescents concomitantly with the combined tetanus, diphtheria, and acellular pertussis vaccine (Boostrix, GlaxoSmithKline Biologicals, Rixensart, Belgium) and the quadrivalent human papillomavirus vaccine (Gardasil, Merck & Co., Inc., Whitehouse Station, NJ).

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.

Randomized trial to assess the immunogenicity, safety and antibody persistence up to three years after a single dose of a tetravalent meningococcal serogroups A, C, W-135 and Y tetanus toxoid conjugate vaccine in toddlers

Effective vaccines offering broad protection to toddlers, who are at high risk for invasive meningococcal disease, are needed. Here, the immunogenicity, safety and antibody persistence of the tetravalent meningococcal ACWY tetanus toxoid conjugate vaccine (MenACWY-TT) were evaluated in toddlers. Healthy participants aged 12 to 23 mo (n = 304) were randomized (3:1) to receive one dose of MenACWY-TT or a monovalent meningococcal serogroup C conjugate vaccine (MenC-CRM₁₉₇). Serum bactericidal activity was evaluated with assays using rabbit (rSBA) and human (hSBA) complement up to three years post-vaccination. MenACWY-TT was demonstrated to be non-inferior to MenC-CRM₁₉₇ in terms of immunogenicity to serogroup C, and the pre-specified immunogenicity criteria for serogroups A, W-135 and Y were met. Exploratory analyses suggested that rSBA geometric mean titers (GMTs), hSBA GMTs and proportions of toddlers with rSBA titers ≥ 1:128 and hSBA titers ≥ 1:4 and ≥ 1:8 were higher for all serogroups at one month post-vaccination with MenACWY-TT compared with MenC-CRM₁₉₇. At three years post-vaccination, at least 90.8% and 73.6% of MenACWY-TT recipients retained rSBA titers ≥ 1:8 for all serogroups and hSBA titers ≥ 1:4 for serogroups C, W-135 and Y, respectively, but the percentages of toddlers with hSBA titers ≥ 1:4 for serogroup A decreased to 21.8%. In both groups, grade 3 adverse events were infrequently reported and no serious adverse events were considered causally related to vaccination. These results suggest that one single dose of MenACWY-TT induces a robust and persistent immune response and has an acceptable safety profile in toddlers. This study has been registered at www.clinicaltrials.gov NCT00427908.

A randomized trial to assess safety and immunogenicity of alternative formulations of a quadrivalent meningococcal (A, C, Y, and W-135) tetanus protein conjugate vaccine in toddlers

BACKGROUND

Neisseria meningitidis is a leading cause of meningitis and septicemia globally. Recent shifts in serogroup dominance in some settings highlight the desirability of polysaccharide-conjugate vaccines with broader meningococcal coverage than serogroup C vaccines in widespread use.

METHODS

We assessed the safety and immunogenicity of a single dose of meningococcal quadrivalent (A, C, W-135, Y) tetanus conjugate vaccine (TetraMen-T), administered at 1 year of age. A total of 378 children were randomized to 1 of 6 groups--5 received alternative formulations of TetraMen-T, the sixth licensed adjuvanted serogroup C conjugate vaccine (Neisvac-C). Solicited adverse event reports were collected from day 0 to 7 after vaccination and unsolicited and serious adverse event reports throughout study participation. Immunogenicity was assessed by serum bactericidal assays containing either a human (hSBA) or baby rabbit (rSBA) complement source before and 1 month after immunization.

RESULTS

All vaccine formulations were safe and well tolerated. Using the various measures of immunogenicity, no consistent relationships were observed between the dose of either polysaccharide or carrier and serogroup-specific response for any one antigen. The highest-dose vaccine provided optimal coverage for all 4 serogroups, with the percentage of recipients achieving hSBA titers ≥ 8 against each as follows: A, 92%; C, 96%; W-135, 71%; Y, 82% (corresponding proportions with rSBAs titers >8 all exceeded 90%). The investigational vaccines were less immunogenic against the serogroup C capsular polysaccharide than the licensed comparator.

CONCLUSIONS

Studies are ongoing that will help to identify optimal scheduling of quadrivalent meningococcal conjugate vaccines, to facilitate their inclusion into national immunization programs seeking extended serogroup coverage against meningococci.

A tetravalent meningococcal serogroups A, C, W-135, and Y tetanus toxoid conjugate vaccine is immunogenic and well-tolerated when co-administered with Twinrix(®) in subjects aged 11-17 years: an open, randomised, controlled trial

The co-administration of the tetravalent meningococcal conjugate vaccine, MenACWY-TT, with a licensed hepatitis A and B vaccine, HepA/B (Twinrix(®)), was compared to their separate administration in this open, randomised, controlled study. Healthy subjects 11-17 years of age (n=611) were randomised (3:1:1) to receive both vaccines, MenACWY-TT alone or HepA/B alone. The co-administration of both vaccines was shown to be non-inferior to their individual administration. At seven months after the first vaccination, 99.4-100% of the subjects who received both vaccines co-administered showed seroprotection against all meningococcal serogroups and at least 99.1% of them were seropositive for hepatitis A and seroprotected against hepatitis B. This study suggests that MenACWY-TT vaccine could be co-administered with HepA/B without adversely impacting the immunogenicity, safety and reactogenicity of either of the vaccines.

Correlation between serum bactericidal activity against Neisseria meningitidis serogroups A, C, W-135 and Y measured using human versus rabbit serum as the complement source

The surrogate of protection against invasive meningococcal disease is the presence of serum bactericidal activity (SBA) at a titer ≥4 in an assay using human serum as the complement source (hSBA). However, for various practical and logistical reasons, many meningococcal vaccines in use today were licensed based on a modified SBA assay that used baby rabbit serum as the complement source (rSBA). To assess the strength of correlation between the two assay systems for serogroups A, C, W-135 and Y, we analyzed a subset of samples from adolescent subjects enrolled in a Phase II study of Novartis' MenACWY-CRM conjugate vaccine vs. an ACWY polysaccharide vaccine; samples were analyzed in parallel using hSBA and rSBA. We compared geometric mean titers (GMTs), calculated Pearson correlation coefficients between paired hSBA and rSBA results, and calculated sensitivity/specificity and likelihood ratios for an rSBA ≥8 or ≥128 for classifying hSBA ≥4, taking hSBA as the 'gold standard'. Correlations between hSBA and rSBA ranged from 0.46 to 0.78 for serogroup C, but were weaker for serogroups A, W-135 and Y (range -0.15 to 0.57). In post vaccination samples, nearly all subjects had rSBA titers ≥8, though up to 15% remained seronegative by hSBA. In post vaccination settings, rSBA titers at ≥8 or ≥128 was highly sensitive for an hSBA titer ≥4, but non-specific. In conclusion, results generated by rSBA did not accurately classify serostatus according to hSBA for serogroups A, W-135 and Y.

Critical appraisal of a quadrivalent CRM(197) conjugate vaccine against meningococcal serogroups A, C W-135 and Y (Menveo) in the context of treatment and prevention of invasive disease

Worldwide, invasive meningococcal disease affects about 500,000 people annually. Case fatality in developed countries averages 10%, and higher rates are reported in less prosperous regions. According to the World Health Organization, the most important pathogenic serogroups are A, B, C, W-135, X, and Y. Clinical features of invasive meningococcal disease make diagnosis and management difficult. Antibiotic measures are recommended for prophylaxis after exposure and for treatment of invasive meningococcal disease cases; however, resistant strains may be emerging. Vaccines are generally regarded as the best preventative measure for invasive meningococcal disease. Polysaccharide vaccines against serogroups A, C, W-135, and Y using protein conjugation technology have clear advantages over older plain polysaccharide formulations without a protein component. The first quadrivalent meningococcal conjugate vaccine (MenACWY-D) was licensed in the US in 2005. More recently, MenACWY-CRM (Menveo^®) was licensed in Europe, the US, the Middle East, and Latin America. MenACWY-CRM uses cross-reactive material 197, a nontoxic mutant of diphtheria toxin, as the carrier protein. MenACWY-CRM offers robust immunogenicity in all age groups, with a tolerability profile similar to that of a plain polysaccharide vaccine. Given its potential for protecting persons from infancy to old age, MenACWY-CRM offers the opportunity to protect broad populations against invasive meningococcal disease. The most optimal strategy for use of the vaccine has to be assessed country by country on the basis of local epidemiology, individual health care systems, and need.

Measurement of functional anti-meningococcal serogroup a activity using strain 3125 as the target strain for serum bactericidal assay

Functional anti-N. meningitidis serogroup A (MenA) activity in human serum is detected by serum bactericidal assay (SBA), using either rabbit (rSBA) or human (hSBA) complement, with F8238 as the recommended MenA SBA target strain. However, the F8238 strain may not be optimal for this purpose because, as we show here, it expresses the L11 immunotype, whereas most MenA invasive strains express the L(3,7)9 or L10 immunotype. Moreover, SBA results may be strain dependent, because immunotypes differ in their sensitivity to complement, emphasizing the need to choose the most appropriate strain. Sera from random subsets of infants, toddlers, children, and adolescents in clinical trials of MenA conjugate vaccines were tested by rSBA using strains 3125 (L10) and F8238 (L11). In unvaccinated subjects from all age groups, the percentages of seropositive samples (rSBA-MenA titer, ≥1:8) was lower using strain 3125 than using strain F8238. However, in toddlers and adolescents immunized with a conjugate MenA vaccine, the percentages of seropositive samples generally were similar using either strain in the rSBA. In two studies, sera also were tested with hSBA. Using hSBA, the differences in the percentages of seroprotective samples (hSBA-MenA titer, ≥1:4) between strains 3125 and F8238 was less apparent, and in contrast with rSBA, the percentage of seroprotective samples from unvaccinated subjects was slightly higher using strain 3125 than using strain F8238. In adults vaccinated with plain MenA polysaccharide, the percentage of seroprotective samples was higher using strain 3125 than with strain F8238, and the vaccine response rates using strain 3125 were better aligned with the demonstrated efficacy of MenA vaccination. In conclusion, SBA results obtained using the MenA L10 3125 strain better reflected vaccine-induced immunity.

Immunogenicity and safety of an investigational quadrivalent meningococcal ACWY tetanus toxoid conjugate vaccine in healthy adolescents and young adults 10 to 25 years of age

BACKGROUND

An investigational quadrivalent Neisseria meningitidis serogroups A, C, W-135, and Y tetanus toxoid conjugate vaccine (MenACWY-TT) has been developed to expand available options for vaccination against invasive meningococcal disease.

METHODS

A total of 784 healthy adolescents and young adults 11 to 25 years of age were randomized (3:1) to receive a single dose of the MenACWY-TT vaccine or a licensed MenACWY diphtheria toxoid conjugate vaccine (MenACWY-DT). An additional nonrandomized group of 88 subjects 10 years of age received the MenACWY-TT vaccine only (MenACWY-TT/10). Immunogenicity was assessed 1 month postvaccination by human complement serum bactericidal assay (hSBA) for all serogroups. Solicited local and general symptoms were recorded for 8 days postvaccination and safety outcomes for 6 months.

RESULTS

One month postvaccination, 81.9% to 96.1% of subjects had hSBA titers ≥ 1:8 in the MenACWY-TT group compared with 70.7% to 98.8% in the MenACWY-DT group. Exploratory analyses showed the proportion of subjects with hSBA titers ≥ 1:4 and ≥ 1:8 to be higher in the MenACWY-TT group than in the MenACWY-DT group for serogroups A, W-135, and Y. GMTs adjusted for age strata and baseline titer 1 month postvaccination were higher in the MenACWY-TT group than in the MenACWY-DT group for all 4 serogroups. The percentage of subjects reporting solicited local and general symptoms of any or Grade 3 severity or serious adverse events was similar between the 2 groups. Immune response and reactogenicity in the MenACWY-TT/10 group was similar to that in the MenACWY-TT group, except for higher hSBA-MenA GMTs in the MenACWY-TT/10 group.

CONCLUSIONS

The investigational MenACWY-TT vaccine was immunogenic in adolescents and young adults, with an acceptable safety profile.

Evaluation of the immunogenicity and biological activity of the Citrobacter freundii Vi-CRM197 conjugate as a vaccine for Salmonella enterica serovar Typhi

Typhoid fever remains a major health problem in developing countries. Young children are at high risk, and a vaccine effective for this age group is urgently needed. Purified capsular polysaccharide from Salmonella enterica serovar Typhi (Vi) is licensed as a vaccine, providing 50 to 70% protection in individuals older than 5 years. However, this vaccine is ineffective in infants. Vi conjugated to a carrier protein (i.e., an exoprotein A mutant from Pseudomonas aeruginosa [rEPA]) is highly immunogenic, provides long-term protection, and shows more than 90% protective efficacy in children 2 to 5 years old. Here, we describe an alternative glycoconjugate vaccine for S. Typhi, Vi-CRM(197), where Vi was obtained from Citrobacter freundii WR7011 and CRM(197), the mutant diphtheria toxin protein, was used as the carrier. We investigated the optimization of growth conditions for Vi production from C. freundii WR7011 and the immunogenicity of Vi-CRM(197) conjugates in mice. The optimal saccharide/protein ratio of the glycoconjugates was identified for the best antibody production. We also demonstrated the ability of this new vaccine to protect mice against challenge with Vi-positive Salmonella enterica serovar Typhimurium.

Meningococcal quadrivalent (serogroups A, C, w135, and y) conjugate vaccine (Menveo): in adolescents and adults

Menveo is a quadrivalent meningococcal polysaccharide conjugate vaccine containing the four Neisseria meningitidis capsular polysaccharides, A, C, W135, and Y, each conjugated to the mutant diphtheria toxin, known as crossreactive material 197 (CRM(197)). Administration of a single dose of the Menveo vaccine elicited a strong immune response against all four vaccine serogroups in adolescents and adults in randomized, single- or multicenter, phase II or III trials. In adolescents, Menveo was generally more immunogenic against vaccine serogroups than the polysaccharide conjugate vaccine Menactra or the unconjugated polysaccharide vaccine Menomune, in terms of seroresponse and/or seroprotection rates and geometric mean titers (GMTs) 1 month post-vaccination in two phase II or III studies. In two phase III trials in adults aged 19-55 years, the immunogenicity of Menveo was generally noninferior or superior to that of Menactra against all four vaccine serogroups, with regard to seroresponse/seroprotection rates, and GMTs 1 month after vaccination. Moreover, an exploratory arm of one of these studies suggested Menveo was at least as immunogenic as Menomune in adults aged 56-65 years. Longer term, the immunogenicity of Menveo persisted for 12-22 months post-vaccination in the adolescent studies, with the vaccine generally remaining at least as immunogenic as Menactra or Menomune. Coadministration of Menveo with a combined tetanus, reduced diphtheria, and acellular pertussis (Tdap) vaccine or Tdap and human papillomavirus vaccines generally did not affect the immunogenicity of these vaccines in adolescents and young adults in two additional randomized, single- or multicenter, phase III studies. The tolerability profile of Menveo was generally similar to that of the comparator vaccines Menactra or Menomune in adults and adolescents, and few Menveo recipients experienced serious adverse events within 30 days or 6 months post-vaccination.

Novel quadrivalent meningococcal A, C, W-135 and Y glycoconjugate vaccine for the broader protection of adolescents and adults

Meningococcal meningitis and septicemia are a persistent public health concern owing to the associated mortality and devastating long-term sequelae. People of all ages may be affected, with the disease burden being higher in at-risk groups. Vaccination is the most rational approach to the prevention of invasive meningococcal disease. A novel quadrivalent meningococcal (Men) serogroup A, C, W-135 and Y polysaccharide–protein conjugate vaccine (MenACWY-CRM), has recently been licensed for use in individuals aged at least 11 years old in the USA, Canada and Europe. One dose of MenACWY-CRM is well tolerated, and induces robust immunity to all constituent vaccine serogroups in 11–65 year old individuals. MenACWY-CRM was found to be noninferior to the quadrivalent meningococcal ACWY-diphtheria toxoid glycoconjugate vaccine, which is also licensed in the USA and Canada. In Europe, MenACWY-CRM is the first quadrivalent meningococcal glycoconjugate vaccine available to provide broader protection against Neisseria meningitidis serogroups A, C, W-135 and Y.

Broad vaccine coverage predicted for a bivalent recombinant factor H binding protein based vaccine to prevent serogroup B meningococcal disease

Factor H binding proteins (fHBP), are bacterial surface proteins currently undergoing human clinical trials as candidate serogroup B Neisseria meningitidis (MnB) vaccines. fHBP protein sequences segregate into two distinct subfamilies, designated A and B. Here, we report the specificity and vaccine potential of mono- or bivalent fHBP-containing vaccines. A bivalent fHBP vaccine composed of a member of each subfamily elicited substantially broader bactericidal activity against MnB strains expressing heterologous fHBP than did either of the monovalent vaccines. Bivalent rabbit immune sera tested in serum bactericidal antibody assays (SBAs) against a diverse panel of MnB clinical isolates killed 87 of the 100 isolates. Bivalent human immune sera killed 36 of 45 MnB isolates tested in SBAs. Factors such as fHBP protein variant, PorA subtype, or MLST were not predictive of whether the MnB strain could be killed by rabbit or human immune sera. Instead, the best predictor for killing in the SBA was the level of in vitro surface expression of fHBP. The bivalent fHBP vaccine candidate induced immune sera that killed MnB isolates representing the major MLST complexes, prevalent PorA subtypes, and fHBP variants that span the breadth of the fHBP phylogenetic tree. Importantly, epidemiologically prevalent fHBP variants from both subfamilies were killed.

Optimizing protection against meningococcal disease

Neisseria meningitidis is a leading cause of bacterial meningitis and septicemia in the United States. Vaccines directed against meningococcal disease must elicit high and persistent titers of bactericidal antibodies against prevalent meningococcal serogroups and be highly efficacious in preventing meningococcal infection. Currently, 2 quadrivalent (A, C, W-135, Y) vaccines-a polysaccharide meningococcal vaccine and a conjugate meningococcal vaccine-are licensed in the United States. Neither is approved for use in infants or toddlers younger than 2 years of age. Results of studies with an investigational quadrivalent (ACWY) meningococcal CRM(197) glycoconjugate vaccine in infants demonstrate that this vaccine has potential to protect this age group. The availability of an effective vaccine for routine universal infant immunization is particularly important because the incidence of invasive meningococcal disease is greatest in infants for all serogroups and because achievable vaccination rates are much greater for infants and young children than they are for adolescents.