Immunogenicity and safety of a quadrivalent meningococcal serogroups A, C, W-135 and Y tetanus toxoid conjugate vaccine (MenACWY-TT) administered to adults aged 56 Years and older: results of an open-label, randomized, controlled trial

Immunogenicity and safety of a quadrivalent meningococcal conjugate vaccine (MenACYW-TT) administered as a booster to adults aged ≥59 years: A phase III randomized study

This 2-stage Phase III study (NCT04142242) of a recently licensed quadrivalent meningococcal tetanus toxoid-conjugate vaccine (MenACYW-TT) assessed the safety and immunogenicity of a booster dose in older adults (≥59 years) primed with either MenACYW-TT or a quadrivalent meningococcal polysaccharide vaccine (MPSV4). Immune persistence of MenACYW-TT and MPSV4 after primary vaccination was also evaluated. During Stage I, the participants administered MPSV4 (n = 165) or MenACYW-TT (n = 236) 3 years previously were randomized 9:2 to receive either a MenACYW-TT booster or to have blood drawn for persistence only. Participants primed with MPSV4 or MenACYW-TT 6-7 years previously had blood drawn for antibody persistence only. A serum bactericidal assay using human complement was used to measure functional antibodies against each serogroup at baseline and, for those receiving a booster, 30 days post-vaccination (D30). Proportions of participants with seroresponse (post-vaccination titers ≥1:16 when baseline titers <1:8 or ≥ 4-fold increase when baseline titers ≥1:8) were determined. Safety data were collected up to D30. Seroresponse rates for all serogroups at D30 ranged from 49.2% to 60.8% in the MPSV4-primed group, and 79.3-93.1% in the MenACYW-TT-primed group. MenACYW-TT induced sufficient seroresponses in each primed group. Geometric mean titers (GMTs) for serogroups C, W, and Y remained or trended higher than pre-vaccination levels at both 3 and 6-7 years after primary vaccination, indicating immune persistence. Safety outcomes were comparable between groups. A MenACYW-TT booster was immunogenic and well tolerated in participants aged ≥59 years regardless of previous quadrivalent meningococcal vaccine received. The greatest immune responses occurred in those primed with MenACYW-TT.

Clinical trial and postmarketing safety experience with MenACWY-TT, a meningococcal group A, C, W, and Y tetanus conjugate vaccine

BACKGROUND

The meningococcal serogroups A, C, W, and Y tetanus toxoid conjugate vaccine (MenACWY-TT; Nimenrix®; Pfizer Ltd, Sandwich, Kent, UK) is licensed in more than 80 countries worldwide for the prevention of meningococcal disease caused by serogroups A, C, W, and Y in individuals throughout their lifespans. This report summarizes safety data from the MenACWY-TT clinical development program and postmarketing experience.

METHODS

Within the clinical study program, reactogenicity data were based on 3 primary studies, including a large pooled analysis across multiple age groups, and long-term safety data were derived from 3 studies evaluating long-term antibody persistence. Postmarketing safety data through April 19, 2021, were collected and analyzed in connection with the MenACWY-TT Periodic Safety Update Report.

RESULTS

Approximately 32 million doses of MenACWY-TT have been administered worldwide, with more than 21,530 additional individuals receiving MenACWY-TT as part of clinical trials. The safety profile of MenACWY-TT was consistent between the clinical study program and the postmarketing experience, as well as with other licensed meningococcal vaccines. The most commonly observed adverse events (AEs) were pyrexia/fever, headache, injection site pain/reactions, nausea/vomiting, and fatigue; serious AEs were rare relative to the number of doses administered. Several cases of serogroup replacement/lack of efficacy were observed in the 1-year postmarketing period but did not appear to be related to MenACWY-TT use.

CONCLUSION

Extensive data derived from clinical trials and postmarketing experience indicate a consistently favorable safety profile for MenACWY-TT across a wide range of age groups.

Trends in Adult and Elderly Vaccination: Focus on Vaccination Practices in Tunisia and Morocco

Vaccine preventable diseases (VPDs) are a prevailing concern among the adult population, despite availability of vaccines. Unlike pediatric vaccination programs, adult vaccination programs lack the required reach, initiative, and awareness. Clinical studies and real-world data have proven that vaccines effectively reduce the disease burden of VPDs and increase life expectancy. In Tunisia and Morocco, the national immunization program (NIP) focuses more on pediatric vaccination and have limited vaccination programs for adults. However, some vaccination campaigns targeting adults are organized. For example, influenza vaccination campaigns prioritizing at risk adults which includes healthcare professionals, elderly, and patients with comorbidities. Women of childbearing age who have never been vaccinated or whose information is uncertain are recommended to receive tetanus vaccination. Tunisia NIP recommends rubella vaccine mainly for women of childbearing age, while in Morocco, national vaccination campaigns were organized for girls and women (up to 24 years of age) to eliminate rubella. Further, travelers from both countries are recommended to follow all requirements and recommendations in the travel destination. The objective of this manuscript is to provide an overview of the global disease burden of common VPDs including (but not limited to) meningococcal diseases, pneumococcal diseases, hepatitis, and influenza. The review also provides an overview of clinical data and guidelines/recommendations on adult vaccination practices, with special focus on Tunisia and Morocco. Some European and North American countries have concrete recommendations and strategies for adult vaccination to keep the VPDs in check. In Morocco and Tunisia, although, there are sporadic adult vaccination initiatives, the efforts still need upscaling and endorsements to boost vaccination awareness and uptake. There is a need to strengthen strategies in both countries to understand the disease burden and spread awareness. Additional studies are needed to generate economic evidence to support cost-effectiveness of vaccines. Integration of private and public healthcare systems may further improve vaccination uptake in adults.

Vaccines and Senior Travellers

Background: International tourist travel has been increasingly steadily in recent years, and looks set to reach unprecedented levels in the coming decades. Among these travellers, an increasing proportion is aged over 60 years, and is healthy and wealthy enough to be able to travel. However, senior travellers have specific risks linked to their age, health and travel patterns, as compared to their younger counterparts.

Methods: We review here the risk of major vaccine-preventable travel-associated infectious diseases, and forms and efficacy of vaccination for these diseases.

Results: Routine vaccinations are recommended for older persons, regardless of whether they travel or not (e.g., influenza, pneumococcal vaccines). Older individuals should be advised about the vaccines that are recommended for their age group in the framework of the national vaccination schedule. Travel-specific vaccines must be discussed in detail on a case-by-case basis, and the risk associated with the vaccine should be carefully weighed against the risk of contracting the disease during travel. Travel-specific vaccines reviewed here include yellow fever, hepatitis, meningococcal meningitis, typhoid fever, cholera, poliomyelitis, rabies, Japanese encephalitis, tick-borne encephalitis and dengue.

Conclusion: The number of older people who have the good health and financial resources to travel is rising dramatically. Older travellers should be advised appropriately about routine and travel-specific vaccines, taking into account the destination, duration and purpose of the trip, the activities planned, the type of accommodation, as well as patient-specific characteristics, such as health status and current medications.

Different Long-Term Duration of Seroprotection against Neisseria meningitidis in Adolescents and Middle-Aged Adults after a Single Meningococcal ACWY Conjugate Vaccination in The Netherlands

Neisseria meningitidis is often asymptomatically carried in the nasopharynx but may cause invasive meningococcal disease, leading to morbidity and mortality. Meningococcal conjugate vaccinations induce functional protective antibodies against capsular antigens, but seroprotection wanes over time. We measured functional antibody titers five years after administration of a single dose of the meningococcal ACWY-polysaccharide-specific tetanus toxoid-conjugated (MenACWY-TT) vaccine in adolescents and middle-aged adults in the Netherlands, using the serum bactericidal antibody with baby rabbit complement (rSBA) assay. Protection was defined as rSBA titer ≥8. The meningococcal ACWY-specific serum IgG concentrations were measured with a multiplex immunoassay. Duration of protection was estimated by a bi-exponential decay model. Sufficient protection for MenC, MenW, and MenY was achieved in 94–96% of the adolescents five years postvaccination, but, in middle-aged adults, only in 32% for MenC, 65% for MenW and 71% for MenY. Median duration of protection for MenCWY was 4, 14, and 21 years, respectively, in middle-aged adults, while, in adolescents, it was 32, 98, and 33 years. Our findings suggest that adolescents, primed in early childhood with MenC conjugate vaccination, remain sufficiently protected after a single dose of MenACWY-TT vaccine. Middle-aged adults without priming vaccination show fast waning of antibodies, particularly MenC, for which protection is lost after four years.

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.

Study of the Immune Response in the Elderly: Is It Necessary to Develop a Vaccine against Neisseria meningitidis for the Aged?

Literature reports the association between aging and decline in the immune system function. The elderly have a higher risk of developing infectious diseases and are often less responsive to vaccines that are effective in the young. The case fatality rate of invasive meningococcal disease is higher in the elderly; therefore, vaccination for this population should be evaluated. Although new vaccines have been developed against Neisseria meningitidis, there is still a need to evaluate a vaccine for those older than 60 years, as the currently licensed vaccines are not indicated for this population.

Immunogenicity and safety of meningococcal group A, C, W and Y tetanus toxoid conjugate vaccine: review of clinical and real-world evidence

Protection by meningococcal group A, C, W and Y (MenACWY) vaccines against four meningococcal disease-causing serogroups is increasingly important because of changing epidemiologic patterns of meningococcal disease, including recent meningococcal serogroup W outbreaks/disease clusters. The MenACWY vaccine conjugated to tetanus toxoid (MenACWY-TT) has been extensively evaluated across the age spectrum (age ≥6 weeks) in randomized Phase II and III and in postmarketing studies. Results support the robust immunogenicity of MenACWY-TT across ages and coadministration with other vaccines. The safety profile is similar regardless of age, primary versus booster vaccination, or concomitant administration; local (swelling, pain, redness) and systemic (fever, fatigue, headache, drowsiness, loss of appetite, irritability) reactogenicity events are most common. These data support use of MenACWY-TT to protect against MenACWY disease.

A review of complement sources used in serum bactericidal assays for evaluating immune responses to meningococcal ACWY conjugate vaccines

Invasive meningococcal disease is rare and potentially devastating but often vaccine-preventable. Evaluation of meningococcal vaccine effectiveness is impractical owing to relatively low disease incidence; protection is therefore estimated using serum bactericidal antibody (SBA) assays. Original experiments on natural immunity established a titer of ≥4 as the correlate of protection for SBA assays using human complement (hSBA), but human complement is relatively difficult to obtain and standardize. Use of baby rabbit complement (rSBA assays), per standard guidelines for serogroups A and C, generally results in comparatively higher titers. Postlicensure effectiveness data for serogroup C conjugate vaccines support acceptance of rSBA titers ≥8 as the correlate of protection for this serogroup, but no thresholds have been formally established for serogroups A, W, and Y. Studies evaluating MenACWY-TT (Nimenrix®; Pfizer Inc, Sandwich, UK) immunogenicity have used both hSBA and rSBA assays, and ultimately suggest that rSBA may be more appropriate for these measurements.

Meningococcal Quadrivalent Tetanus Toxoid Conjugate Vaccine (MenACWY-TT; Nimenrix®): A Review

MenACWY-TT (Nimenrix^®) is a quadrivalent meningococcal tetanus toxoid conjugate vaccine licensed in Europe for active immunisation of individuals aged ≥ 6 weeks against invasive disease caused by Neisseria meningitidis capsular groups A, C, W and Y. MenACWY-TT is the first quadrivalent conjugate vaccine to be approved in Europe for use in infants as young as 6 weeks of age. Numerous phase II-IIIb clinical studies showed that intramuscular MenACWY-TT administered as primary or booster vaccination was highly immunogenic for all four vaccine capsular groups and had an acceptable reactogenicity profile in individuals aged 6 weeks to ≥ 56 years. MenACWY-TT is as immunogenic and safe as other previously licensed monovalent capsular group C or quadrivalent capsular groups A, C, W and Y meningococcal vaccines and can be coadministered with other routine vaccines without adversely affecting the immunogenicity or safety profiles of either vaccine. Current data indicate that primary and booster vaccination with MenACWY-TT is a valuable and safe option for broadening meningococcal protection against four capsular groups across a broad age range, starting as early as 6 weeks of age.

Novel Intervention in the Aging Population: A Primary Meningococcal Vaccine Inducing Protective IgM Responses in Middle-Aged Adults

Introduction

Vaccine responses are often reduced in the elderly, leaving part of the elderly population vulnerable to infectious diseases. Timely vaccination may offer a solution for strengthening memory immunity before reaching old age, which classifies middle-aged persons as a target age group for vaccine interventions. However, knowledge regarding the immunogenicity of primary immunizations in middle-aged adults is lacking. We determined the immunogenicity of a primary meningococcal vaccine towards which no or (very) low pre-vaccination immunity exists in middle-aged adults (NTR4636).

Methods

A vaccine containing multiple meningococcal groups (tetravalent) conjugated to tetanus toxoid (MenACWY-TT) was administered to middle-aged adults (50–65 years of age, N = 204) in a phase IV single-center and open-label study. Blood samples were taken pre-, 7 days, 28 days, and 1 year post-vaccination. Functional antibody titers were measured with the serum bactericidal assay (SBA). Meningococcal- and tetanus-specific antibody responses were determined with a fluorescent bead-based multiplex immunoassay. A bi-exponential decay model was used to estimate long-term protection.

Results

In the majority of the participants, the meningococcal vaccine clearly induced naïve responses to meningococci W (MenW) and meningococci Y (MenY) as compared to a booster response to meningococci C (MenC). After 28 days, 94, 99, and 97% of the participants possessed a protective SBA titer for MenC, MenW, and MenY, respectively, which was maintained in 76, 94, and 86% 1 year post-vaccination. At this 1-year time point, significantly lower SBA titers were found in participants without a pre-vaccination SBA titer. Overall, protective antibody titers were predicted to persist after 10 years in 40–60% of the participants. The SBA titers correlated well with the meningococcal-specific IgM responses, especially for MenW and MenY. Interestingly, these IgM responses were negatively correlated with age.

Conclusion

Primary immunization with a tetravalent meningococcal vaccine was highly immunogenic in middle-aged adults, inducing protective antibody titers in the vast majority of the participants lasting for at least 1 year. The age-related decrease in highly functional IgM responses argues in favor of vaccination against de novo antigens before reaching old age and, hence, middle-aged persons are an age group of interest for future vaccine interventions to protect the aging population.

Polysaccharide conjugate vaccine protein carriers as a "neglected valency" - Potential and limitations

The development of vaccines against polysaccharide-encapsulated pathogens (e.g. Haemophilus influenzae type b, pneumococci, meningococci) is challenging because polysaccharides do not elicit a strong and long-lasting immune response (i.e. T-cell independent). This can be overcome by conjugating the polysaccharide to a protein carrier (e.g. tetanus toxoid, cross-reacting material 197 [CRM]), which vastly improves the immune response and induces memory to the polysaccharide (T-cell dependent). Although it is well documented that protein carriers additionally induce an immune response against themselves, this potential "additional valency" has so far not been recognized. The only exception is for the protein D carrier (derived from non-typeable Haemophilus influenzae [NTHi]) used in a pneumococcal conjugate vaccine, which may have a beneficial impact on NTHi acute otitis media. In this review, we describe the immunogenicity of various protein carriers and discuss their potential dual function: as providers of T-cell helper epitopes and as protective antigens. If this "additional valency" could be proven to be protective, it may be possible to consider its potential effect on the number of required immunizations. We also describe the potential for positive or negative interference between conjugate vaccines using the same protein carriers, the resulting desire for novel carriers, and information on potential new carriers. The range of conjugate vaccines is ever expanding, with different carriers and methods of conjugation. We propose that new conjugate vaccine trials should assess immunogenicity to both the polysaccharide and carrier. Ultimately, this so-far "neglected valency" could be an exploitable characteristic of polysaccharide conjugate vaccines.

Safety and Immunogenicity of the Quadrivalent Meningococcal Serogroups A, C, W and Y Tetanus Toxoid Conjugate Vaccine Coadministered With Routine Childhood Vaccines in European Infants: An Open, Randomized Trial

BACKGROUND

This was the first study evaluating the immunogenicity and safety of the quadrivalent meningococcal tetanus toxoid conjugate vaccine (MenACWY-TT) coadministered with routine childhood vaccines in young infants.

METHODS

In this open, randomized, controlled, phase III study (NCT01144663), 2095 infants (ages 6-12 weeks) were randomized (1:1:1:1) into 4 groups to receive MenACWY-TT at 2, 3, 4 and 12 months of age, or MenACWY-TT, MenC-cross-reactive material (CRM197) or MenC-TT at 2, 4 and 12 months of age. All participants received PHiD-CV and DTPa-HBV-IPV/Hib at 2, 3, 4 and 12 months of age. Immune responses were measured by serum bactericidal activity assays using rabbit (rSBA) and human (hSBA) complement. Solicited and unsolicited symptoms were recorded during 8 and 31 days post-vaccination, respectively, and serious adverse events throughout the study.

RESULTS

Noninferiority of immune responses to MenC induced by 2 or 3 doses of MenACWY-TT versus 2 doses of MenC-TT or MenC-CRM197 was demonstrated. Predefined criteria for the immunogenicity of MenACWY-TT to MenA, MenW and MenY were met. One month after 2 or 3 primary MenACWY-TT doses, ≥93.1% and ≥88.5% of infants had rSBA and hSBA titers ≥1:8 for all serogroups. The robust increases in rSBA and hSBA titers observed for all vaccine serogroups postbooster vaccination suggested that MenACWY-TT induced immune memory. MenACWY-TT coadministered with childhood vaccines had a clinically acceptable safety profile.

CONCLUSIONS

This study supports the coadministration of MenACWY-TT with routine childhood vaccines as 2 or 3 primary doses during infancy followed by a booster dose in the second year of life.

Vaccination in Hajj: An Overview of the Recent Findings

Background:

About two million people annually travel to Kingdom of Saudi Arabia to perform Hajj. The pilgrims may be at risk of exposure to communicable diseases in this mass gathering and their vaccination against contagious diseases can prevent many morbidities and mortalities. The aim of our study was to review the papers which evaluated effectiveness and compliance of the vaccines applied in Hajj.

Methods:

We used PubMed and Scopus to search international medical databases. The key words were as follows: Hajj, Haj, vaccine, vaccination, and immunization. The time interval of the search was from the beginning of 2010 to May 23, 2016. One hundred and thirty papers were extracted, and their contents were subsequently reviewed after title and abstract screenings. The original articles were included in the study and non-English articles were excluded from the study.

Results:

Considering the extracted papers, almost all pilgrims were vaccinated against meningococcal diseases. Using of influenza and pneumococcal vaccine rates were different among the pilgrims. The other vaccines have been taking according to specific conditions.

Conclusions:

The findings regarding influenza vaccine effectiveness are contradictory. A few studies confirmed the flu vaccine effectiveness while some others rejected its usefulness. Meningococcal immunization is an effective preventive tool with high compliance for Hajj pilgrims. Further investigations are recommended for the other vaccines.

Safety and immunogenicity of the tau vaccine AADvac1 in patients with Alzheimer's disease: a randomised, double-blind, placebo-controlled, phase 1 trial

BACKGROUND

Neurofibrillary pathology composed of tau protein is a main correlate of cognitive impairment in patients with Alzheimer's disease. Immunotherapy targeting pathological tau proteins is therefore a promising strategy for disease-modifying treatment of Alzheimer's disease. We have developed an active vaccine, AADvac1, against pathological tau proteins and assessed it in a phase 1 trial.

METHODS

We did a first-in-man, phase 1, 12 week, randomised, double-blind, placebo-controlled study of AADvac1 with a 12 week open-label extension in patients aged 50-85 years with mild-to-moderate Alzheimer's disease at four centres in Austria. We randomly assigned patients with a computer-generated sequence in a 4:1 ratio overall to receive AADvac1 or placebo. They received three subcutaneous doses of AADvac1 or placebo from masked vaccine kits at monthly intervals, and then entered the open-label phase, in which all patients were allocated to AADvac1 treatment and received another three doses at monthly intervals. Patients, carers, and all involved with the trial were masked to treatment allocation. The primary endpoint was all-cause treatment-emergent adverse events, with separate analyses for injection site reactions and other adverse events. We include all patients who received at least one dose of AADvac1 in the safety assessment. Patients who had a positive IgG titre against the tau peptide component of AADvac1 at least once during the study were classified as responders. The first-in-man study is registered with EU Clinical Trials Register, number EudraCT 2012-003916-29, and ClinicalTrials.gov, number NCT01850238; the follow-up study, which is ongoing, is registered with EU Clinical Trials Register, number EudraCT 2013-004499-36, and ClinicalTrials.gov, number NCT02031198.

FINDINGS

This study was done between June 9, 2013, and March 26, 2015. 30 patients were randomly assigned in the double-blind phase: 24 patients to the AADvac1 group and six to the placebo group. A total of 30 patients received AADvac1. Two patients withdrew because of serious adverse events. The most common adverse events were injection site reactions after administration (reported in 16 [53%] vaccinated patients [92 individual events]). No cases of meningoencephalitis or vasogenic oedema occurred after administration. One patient with pre-existing microhaemorrhages had newly occurring microhaemorrhages. Of 30 patients given AADvac1, 29 developed an IgG immune response. A geometric mean IgG antibody titre of 1:31415 was achieved. Baseline values of CD3+ CD4+ lymphocytes correlated with achieved antibody titres.

INTERPRETATION

AADvac1 had a favourable safety profile and excellent immunogenicity in this first-in-man study. Further trials are needed to corroborate the safety assessment and to establish proof of clinical efficacy of AADvac1.

FUNDING

AXON Neuroscience SE.

Persistence of the immune response two years after vaccination with quadrivalent meningococcal ACWY-tetanus toxoid conjugate vaccine (MenACWY-TT) in Asian adolescents

Invasive meningococcal disease is a serious infection that is most often vaccine-preventable. Long-term protection relies on antibody persistence. Here we report the persistence of the immune response 2 y post-vaccination with a quadrivalent meningococcal serogroups A, C, W, Y tetanus toxoid conjugate vaccine (MenACWY-TT) compared with a MenACWY polysaccharide vaccine (Men-PS), in Asian adolescents aged 11–17 y. We also report a re-analysis of data from the primary vaccination study. This persistence study (NCT00974363) conducted in India and the Philippines included subjects who previously (study NCT00464815) received a single dose of MenACWY-TT or Men-PS. Persistence of functional antibodies was measured in 407 MenACWY-TT recipients and 132 Men-PS recipients (according-to-protocol cohort) using a rabbit complement serum bactericidal assay (rSBA, cut-off 1:8). Vaccine-related serious adverse events (SAEs) occurring since the end of the initial vaccination study were retrospectively recorded. Two y post-vaccination ≥99.3% of adolescents who received MenACWY-TT had persisting antibody titers ≥1:8 against each vaccine serogroup. Antibody persistence was higher (exploratory analysis) in the MenACWY-TT group than the Men-PS group in terms of rSBA titers ≥1:8 for serogroups W and Y; rSBA titers ≥1:128 for serogroups A, W and Y; and rSBA GMTs for serogroups A, W and Y; and was lower in the MenACWY-TT group for rSBA GMTs for serogroup C. No vaccine-related SAEs were reported. The results of this study indicated that antibodies persisted for at least 2 y in the majority of adolescents after vaccination with a single dose of MenACWY-TT.

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.

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.

The Impact of Age on the Efficacy of 13-valent Pneumococcal Conjugate Vaccine in Elderly

In a post hoc analysis of the Community-Acquired Pneumonia (CAP) immunization Trial in Adults the model-predicted 13-valent pneumococcal conjugate vaccine efficacy for preventing vaccine-type specific CAP and Invasive Pneumococcal Disease declined from 65% to 40% for subjects being 65 and 75 year olds at the time of vaccination, respectively.

Immunogenicity of meningococcal quadrivalent (serogroup A, C, W135 and Y) tetanus toxoid conjugate vaccine: systematic review and meta-analysis

Meningococcal meningitis represents one of the leading cause of bacterial meningitis in developed countries. Among the thirteen described serogroups, only five are usually responsible of invasive infections making immunisation against multiple serogroups the best strategy to protect individuals from this disease. Herein we carried out a systematic review and meta-analysis, in accordance with the PRISMA statement, of the recently EU-licensed meningococcal ACWY-tetanus toxoid conjugate vaccine (MenACWY-TT). We included 15 randomised clinical trials, comparing MenACWY-TT and Men-PS (ten studies), MenACWY-TT and MenC-CRM197 (four studies) and MenACWY-TT and MenACWY-DT (one study). All studies included in the meta-analysis showed high immunogenicity for MenACWY-TT vaccines in all tested serogroups. Our results suggest that the MenACWY-TT vaccine is as immunogenic as the other commercial available meningococcal vaccines.

Meningococcal serogroup A, C, W, and Y serum bactericidal antibody profiles in Hajj pilgrims

BACKGROUND

The religious seasons of Hajj and Umra in the Kingdom of Saudi Arabia (KSA) have historically been associated with epidemics of meningococcal disease. Due to the effective preventive measures taken in recent years, including vaccination, no meningococcal outbreaks have been reported during Hajj or were Hajj-associated. However, little is known about the immunological profile of pilgrims. The aim of this study was to assess the immunological profile of pilgrims on arrival in KSA against the four meningococcal serogroups, A, C, W, and Y, contained within the quadrivalent vaccine.

METHODS

Following consent, socio-demographic factors and health-related information was collected from pilgrims arriving at King Abdul Aziz International Airport and a blood sample taken. Antibodies were quantified by serum bactericidal antibody assay using baby rabbit complement (rSBA) against the four meningococcal serogroups, A, C, W, and Y.

RESULTS

Serum samples were collected from 796 pilgrims; rSBA results were obtained for all four serogroups for 741 of these samples. A total of 48 (6.5%) Hajjis had previously attended Hajj, ranging from 1 to 14 times (median 2 times); 98.2% had received meningococcal quadrivalent vaccine in the last 3 years. Of the 13 who had not, all originated from Bangladesh, with four reporting no previous meningococcal vaccination and nine reporting having received the vaccination more than 3 years ago. For serogroup A, only one pilgrim from Indonesia had an rSBA titre <8. For serogroups C, W, and Y, the percentages of pilgrims with rSBA titres <8 were 9.9%, 17.4%, and 9.4%, respectively. Of note was the high prevalence of non-complement-mediated lysis in pilgrims originating from Nigeria (28/47; 59.6%) and Afghanistan (21/47; 44.7%), but not the other countries. This may be a reflection of the type and pattern of antibiotic usage among these communities.

CONCLUSION

The vast majority of pilgrims are vaccinated and protected against meningococcal serogroups A, C, W, and Y.

Meningococcal serogroups A, C, W-135, and Y tetanus toxoid conjugate vaccine: a new conjugate vaccine against invasive meningococcal disease

Invasive meningococcal disease is a serious infection that occurs worldwide. It is caused by Neisseria meningitidis, of which six serogroups (A, B, C, W-135, X, and Y) are responsible for most infections. The case fatality rate of meningococcal disease remains high and can lead to significant sequelae. Vaccination remains the best strategy to prevent meningococcal disease. Polysaccharide vaccines were initially introduced in the late 1960s but their limitations (poor immunogenicity in infants and toddlers and hyporesponsiveness after repeated doses) have led to the development and use of meningococcal conjugate vaccines, which overcome these limitations. Two quadrivalent conjugated meningococcal vaccines – MenACWY-DT (Menactra^®) and MenACWY-CRM₁₉₇ (Menveo^®) – using diphtheria toxoid or a mutant protein, respectively, as carrier proteins have already been licensed in the US. Recently, a quadrivalent meningococcal vaccine conjugated to tetanus toxoid (MenACWY-TT; Nimenrix^®) was approved for use in Europe in 2012. The immunogenicity of MenACWY-TT, its reactogenicity and safety profile, as well as its coadministration with other vaccines are discussed in this review. Clinical trials showed that MenACWY-TT was immunogenic in children above the age of 12 months, adolescents, and adults, and has an acceptable reactogenicity and safety profile. Its coadministration with several other vaccines that are commonly used in children, adolescents, and adults did not affect the immunogenicity of MenACWY-TT or the coadministered vaccine, nor did it affect its reactogenicity and safety. Other studies are now ongoing in order to determine the immunogenicity, reactogenicity, and safety of MenACWY-TT in infants from the age of 6 weeks.

Review of meningococcal vaccines with updates on immunization in adults

Meningococcal disease is a serious and global life-threatening disease. Six serogroups (A, B, C, W-135, X, and Y) account for the majority of meningococcal disease worldwide. Meningococcal polysaccharide vaccines were introduced several decades ago and have led to the decline in the burden of disease. However, polysaccharide vaccines have several limitations, including poor immunogenicity in infants and toddlers, short-lived protection, lack of immunologic memory, negligible impact on nasopharyngeal carriage, and presence of hyporesponsiveness after repeated doses. The chemical conjugation of plain polysaccharide vaccines has the potential to overcome these drawbacks. Meningococcal conjugate vaccines include the quadrivalent vaccines (MenACWY-DT, MenACWY-CRM, and MenACWY-TT) as well as the monovalent A and C vaccines. These conjugate vaccines were shown to elicit strong immune response in adults. This review addresses the various aspects of meningococcal disease, the limitations posed by polysaccharide vaccines, the different conjugate vaccines with their immunogenicity and reactogenicity in adults, and the current recommendations in adults.

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.