Persistence of the immune response at 5 years of age following infant immunisation with investigational quadrivalent MenACWY conjugate vaccine formulations

A Decade of Fighting Invasive Meningococcal Disease: A Narrative Review of Clinical and Real-World Experience with the MenACWY-CRM Conjugate Vaccine

The quadrivalent A, C, W and Y meningococcal vaccine conjugated to nontoxic mutant of diphtheria toxin (MenACWY-CRM) has been licensed since 2010 for the prevention of invasive meningococcal disease (IMD), an uncommon but life-threatening condition. Here, we summarize the experience accrued with MenACWY-CRM during the first decade since its licensure, by providing an overview of clinical trials investigating the safety, immunogenicity and co-administration of MenACWY-CRM with other vaccines as well as presenting real-world evidence regarding the impact of MenACWY-CRM vaccination on carriage and IMD incidence. MenACWY-CRM has demonstrated an acceptable clinical safety profile across a wide range of age groups; no safety concerns have been reported in special populations, such as immunocompromised infants and toddlers, or pregnant women. MenACWY-CRM has also been proven to be immunogenic in various age groups and geographic settings, and a booster dose has been shown to elicit strong anamnestic responses in all studied populations, irrespective of the vaccine used for priming. With no clinically relevant vaccine interactions reported, MenACWY-CRM is being conveniently integrated into existing vaccination programs for various age and risk groups; this possibility of co-administration helps improving vaccine coverage and streamlining the healthcare process of fighting preventable infectious diseases. Vaccination of adolescents and adults has been proven to reduce nasopharyngeal carriage for serogroups C, W and Y, which is an important element in reducing transmission. Real-world evidence indicates that MenACWY-CRM can reduce IMD incidence even in high-exposure groups. When combined with vaccines against serogroup B meningococci, MenACWY-CRM can offer protection against five of the most common serogroups responsible for IMD, which is an important advantage in the continuously evolving landscape of meningococcal serogroup epidemiology.

Invasive meningococcal disease is an uncommon but life-threatening infection that appears as meningitis and/or sepsis. It is caused by Neisseria meningitidis, a bacteria commonly present in the throat or nose. Vaccination with MenACWY-CRM (Menveo, GSK) helps to prevent invasive meningococcal disease caused by four of the most common N. meningitidis serogroups (A, C, W and Y). This vaccine has been licensed for 10 years: we summarized here all available evidence gathered since the vaccine has been available in general practice, from clinical development to real-world experience. Information gained during clinical trials of MenACWY-CRM confirms that vaccination is well tolerated, has an acceptable safety profile and would induce significant protection when given to individuals of various ages such as infants, toddlers, children, adolescents and adults, and when administered at the same time as routine or traveler vaccinations as well as vaccines against serogroup B meningococci (4CMenB). Vaccination with MenACWY-CRM has been shown to decrease the number of serogroup C, W and Y meningococci found in the nose and throat in adolescents and adults as well as the occurrence of invasive meningococcal disease in a high-exposure population from a real-world setting. MenACWY-CRM can conveniently be integrated into most of the existing vaccination schedules for various age and risk groups. When combined with vaccination against serogroup B meningococci, MenACWY-CRM can contribute to providing protection against five of the most common serogroups responsible for invasive meningococcal disease.

The epidemiology of invasive meningococcal disease and the utility of vaccination in Malta

Invasive meningococcal disease (IMD) is a vaccine-preventable devastating infection that mainly affects infants, children and adolescents. We describe the population epidemiology of IMD in Malta in order to assess the potential utility of a meningococcal vaccination programme. All cases of microbiologically confirmed IMD in the Maltese population from 2000 to 2017 were analysed to quantify the overall and capsular-specific disease burden. Mean overall crude and age-specific meningococcal incidence rates were calculated to identify the target age groups that would benefit from vaccination. Over the 18-year study period, 111 out of the 245 eligible notified cases were confirmed microbiologically of which 70.3% had septicaemia, 21.6% had meningitis, and 6.3% had both. The mean overall crude incidence rate was 1.49/100,000 population with an overall case fatality rate of 12.6%. Meningococcal capsular groups (Men) B followed by C were the most prevalent with W and Y appearing over the last 6 years. Infants had the highest meningococcal incidence rate of 18.9/100,000 followed by 6.1/100,000 in 1–5 year olds and 3.6/100,000 in 11–15 year old adolescents. The introduction of MenACWY and MenB vaccines on the national immunization schedule in Malta would be expected to reduce the disease burden of meningococcal disease in children and adolescents in Malta.

Recent changes of invasive meningococcal disease in France: arguments to revise the vaccination strategy in view of those of other countries

In France, the incidence of invasive meningococcal disease (IMD) is around 1/100,000, with the following trends over the 2011-2018 period: a leading role of group B in subjects <15 years, a decrease of group C among <1 year since 2017, an increase of group W in all age groups including subjects <1 year since 2014 and a positive correlation between group Y and age group. In Europe, vaccination progressed with conjugate ACWY vaccines and proteins-based B vaccines. Their benefit-risk-cost balance is however not so obvious for area at low incidence (<2/100,000), explaining tremendous variations between countries, from no recommendation to recommend all available vaccines. In France, the calendar still includes only C with a good adhesion in infants but a fiasco of the catch-up campaign in adolescents and young adults. In Europe, it is time to consider not only national epidemiology but also trends in the neighborhood. The increase of group W cases encourages switching C to ACWY vaccine both in infants and adolescents. It is also time to protect infants with B vaccine. Large pedagogy on the disease is required to increase the adhesion to the vaccination and to recognize and treat earlier the residual cases.

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

Purpose

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

Materials and Methods

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

Results

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

Conclusion

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

Antibody persistence and booster response following MenACWY-CRM vaccination in children as assessed by two different assay methods

BACKGROUND

The quadrivalent meningococcal conjugate vaccine MenACWY-CRM has been shown to be immunogenic and well-tolerated in infants and toddlers. We evaluated antibody persistence for up to 4 years after vaccination with MenACWY-CRM in the first years of life and response to a booster dose administered at 60 months of age.

METHODS

This was phase 3b, open-label, multicenter extension trial (NCT01148017). We assessed by hSBA and rSBA the persistence of antibody responses to serogroups ACWY in 203 healthy 60-month-olds receiving 4 doses of MenACWY-CRM during infancy (ACWY-4 group), or 2 doses at 12/13 and 15 months or 1 dose at 18 months of age (ACWY-2 group). We administered a MenACWY-CRM dose to 224 primed and 45 naïve 60-month-olds and evaluated safety and antibody response 1 month later.

RESULTS

Antibody persistence measured by both assays was higher in primed than naïve 60-month-olds. The percentages of primed children with hSBA titers ≥8 was low for serogroup A (6-25%) and moderate for serogroups C (27-43%), Y (69-74%) and W (56-69%). For all serogroups, hSBA antibody geometric mean titers (GMTs) tended to be higher in the ACWY-2 than the ACWY-4 group. Post-booster/single dose, ≥96% of primed and ≥73% of naïve children had hSBA titers ≥8 against each serogroup, and hSBA GMTs were higher in primed children. The booster dose was well-tolerated and no safety concern was identified. We further assessed persistence using rSBA across different age groups and detected no overall correlation between rSBA and hSBA titers.

CONCLUSIONS

Primary vaccination of infants/toddlers with MenACWY-CRM resulted in moderate antibody persistence against serogroups C, W and Y for up to 4 years after the last priming dose. Regardless of priming schedule, a MenACWY-CRM booster dose at 60 months of age induced a robust immune response against all serogroups and was well-tolerated in all children.

Management of meningococcal outbreaks: are we using the same language? Comparison of the public health policies between high-income countries with low incidence of meningococcal disease

BACKGROUND

Invasive meningococcal disease (IMD) in high-income countries usually occurs sporadically with low incidence and occasionally as small clusters or outbreaks. The WHO guidelines (GLs) for IMD outbreak applies only to African countries with high endemic incidence. Several high-income countries developed their own GLs on IMD outbreak, and we compare their terminology, classification, definitions, and public health interventions.

METHODS

National IMD outbreak GLs of the European Union and the Organisation for Economic Co-operation and Development member states were compared. Due to linguistic barriers, 17 out of forty-one countries were selected, and the GLs on the websites of the national health authorities were independently screened by two researchers.

RESULTS

National GLs on IMD outbreak were available for 12 countries. All GLs classify IMD outbreak into organization and community based using different terminology (cluster, epidemic, etc.). Two GLs introduce also a third condition of hyperendemic. Definitions, thresholds, and countermeasures vary among countries.

CONCLUSIONS

Different definitions of organization and community-based outbreaks and countermeasures are expected because of uncertainties about their effectiveness, and differences between countries in health-care systems and public health policy approaches. Nevertheless, variations in terminology, definitions and countermeasures are confusing and reflect the need for an international standardization.

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.

Update on invasive meningococcal vaccination for Canadian children and youth

Invasive meningococcal disease (IMD) is serious, often resulting in fulminant sepsis or meningitis. IMD in Canada is primarily attributable to serogroups B and C. There are routine programs for serogroup C vaccine at 12 months of age, with some jurisdictions routinely providing additional earlier doses. Adolescents routinely receive a booster dose of serogroup C vaccine or of a quadrivalent (serogroups A, C, W and Y) vaccine. Serogroup B vaccines are not recommended for routine use pending further data on the efficacy and duration of protection from the available vaccine. However, children at increased risk for IMD should start immunization for serogroups B and C as soon as possible, assuming that they are at least 2 months of age.

Antibody persistence and booster responses 24-36 months after different 4CMenB vaccination schedules in infants and children: A randomised trial

OBJECTIVES

This phase IIIb, open-label, multicentre, extension study (NCT01894919) evaluated long-term antibody persistence and booster responses in participants who received a reduced 2 + 1 or licensed 3 + 1 meningococcal serogroup B vaccine (4CMenB)-schedule (infants), or 2-dose catch-up schedule (2-10-year-olds) in parent study NCT01339923.

MATERIALS AND METHODS

Children aged 35 months to 12 years (N = 851) were enrolled. Follow-on participants (N = 646) were randomised 2:1 to vaccination and non-vaccination subsets; vaccination subsets received an additional 4CMenB dose. Newly enrolled vaccine-naïve participants (N = 205) received 2 catch-up doses, 1 month apart (accelerated schedule). Antibody levels were determined using human serum bactericidal assay (hSBA) against MenB indicator strains for fHbp, NadA, PorA and NHBA. Safety was also evaluated.

RESULTS

Antibody levels declined across follow-on groups at 24-36 months versus 1 month post-vaccination. Antibody persistence and booster responses were similar between infants receiving the reduced or licensed 4CMenB-schedule. An additional dose in follow-on participants induced higher hSBA titres than a first dose in vaccine-naïve children. Two catch-up doses in vaccine-naïve participants induced robust antibody responses. No safety concerns were identified.

CONCLUSION

Antibody persistence, booster responses, and safety profiles were similar with either 2 + 1 or 3 + 1 vaccination schedules. The accelerated schedule in vaccine-naïve children induced robust antibody responses.

Five-year Antibody Persistence and Booster Response After 1 or 2 Doses of Meningococcal A, C, W and Y Tetanus Toxoid Conjugate Vaccine in Healthy Children

BACKGROUND

We evaluated antibody persistence up to 5 years postvaccination with a quadrivalent meningococcal serogroups A, C, W and Y tetanus toxoid conjugate vaccine (MenACWY-TT), and subsequent booster responses to MenACWY-TT in healthy US children.

METHODS

In the initial phase II, open, multicenter study (NCT00471081), 349 infants were randomized (1:1) to receive MenACWY-TT (1 or 2 doses). In the follow-up study (NCT00718666), we evaluated antibody persistence at years 1, 3 and 5 by serum bactericidal assay using human complement (hSBA). At year 5, children received a booster dose of MenACWY-TT. We compared their immune responses at 1 month postbooster with those from 100 age-matched, meningococcal naive children, who received a primary MenACWY-TT dose. We recorded solicited adverse events for 4 days and unsolicited adverse events for 31 days, followed by an additional 5-month extended safety follow-up.

RESULTS

At year 5, ≥64.0% of 1-dose and ≥74.6% of 2-dose recipients had hSBA titers ≥8 for MenC, MenW and MenY. For MenA, 31.7% of 1-dose and 38.0% of 2-dose recipients had hSBA titers ≥8. One month postvaccination, all booster dose recipients and ≥78.5% of primary dose recipients exhibited hSBA titers ≥8 for all serogroups. Geometric mean titers were higher in primed than in naive children. MenACWY-TT had a clinically acceptable safety profile.

CONCLUSIONS

With the exception of serogroup W, antibody persistence 5 years after MenACWY-TT vaccination did not differ substantially between children who received 1 or 2 doses in infancy. A booster dose of MenACWY-TT elicited robust anamnestic responses and was well tolerated.

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.

Antibody persistence up to 5 years after vaccination of toddlers and children between 12 months and 10 years of age with a quadrivalent meningococcal ACWY-tetanus toxoid conjugate vaccine

We studied the persistence of serum bactericidal antibody using rabbit and human complement (rSBA/hSBA, cut-offs 1:8) 5 y after a single dose of meningococcal serogroups A, C, W, Y tetanus toxoid conjugate vaccine (MenACWY-TT) compared with age-appropriate control vaccines in toddlers and children (NCT00427908). Children were previously randomized (3:1) to receive either MenACWY-TT or control vaccine (MenC-CRM197 in 1-<2 y olds; MenACWY-polysaccharide vaccine [Men-PS] in 2-<11 y olds). Subjects with rSBA-MenC titers <1:8 at any time point were revaccinated with MenC conjugate vaccine and discontinued from the study. A repeated measurement statistical model assessed potential selection effects due to drop-outs. At year 5 in MenACWY-TT-vaccinated-toddlers for serogroups A, C, W, and Y respectively, percentages with rSBA titers ≥1:8 were 73.5%, 77.6%, 34.7%, and 42.9%, hSBA ≥1:8 were 35.6%, 91.7%, 82.6% and 80.0%. For MenC-CRM197 recipients, 63.6% had persisting rSBA-MenC titers ≥1:8 and 90.9% had hSBA-MenC ≥1:8 (not significantly different versus MenACWY-TT for either assay: exploratory analyses). In 2-<11 y olds rSBA titers ≥1:8 in MenACWY-TT-vaccinees were 90.8%, 90.8%, 78.6%, and 78.6% and 15.4%, 100%, 0.0%, 7.7% in Men-PS-vaccinees (significantly different for serogroups A, W and Y, exploratory analyses). Serogroups A, W and Y rSBA GMTs were ≥ 26-fold higher in MenACWY-TT-vaccinees. As expected, GMTs modeled at year 5 to assess the impact of subject drop out (mainly for revaccination), appeared lower for serogroup C. No vaccine-related SAEs were reported. Antibody persistence was observed for all serogroups up to 5 y after MenACWY-TT vaccination.

Human Infant Memory B Cell and CD4+ T Cell Responses to HibMenCY-TT Glyco-Conjugate Vaccine

Carrier-specific T cell and polysaccharide-specific B cell memory responses are not well characterised in infants following glyco-conjugate vaccination. We aimed to determine if the number of Meningococcal (Men) C- and Y- specific memory B cells and; number and quality of Tetanus Toxoid (TT) carrier-specific memory CD4+ T cells are associated with polysaccharide-specific IgG post HibMenCY-TT vaccination. Healthy infants received HibMenCY-TT vaccine at 2, 4 and 6 months with a booster at 12 months. Peripheral blood mononuclear cells were isolated and polysaccharide-specific memory B cells enumerated using ELISpot. TT-specific memory CD4+ T cells were detected and phenotyped based on CD154 expression and intracellular TNF-α, IL-2 and IFN-γ expression following stimulation. Functional polysaccharide-specific IgG titres were measured using the serum bactericidal activity (SBA) assay. Polysaccharide-specific Men C- but not Men Y- specific memory B cell frequencies pre-boost (12 months) were significantly associated with post-boost (13 months) SBA titres. Regression analysis showed no association between memory B cell frequencies post-priming (at 6 or 7 months) and SBA at 12 months or 13 months. TT-specific CD4+ T cells were detected at frequencies between 0.001 and 0.112 as a percentage of CD3+ T cells, but their numbers were not associated with SBA titres. There were significant negative associations between SBA titres at M13 and cytokine expression at M7 and M12. Conclusion: Induction of persistent polysaccharide-specific memory B cells prior to boosting is an important determinant of secondary IgG responses in infants. However, polysaccharide-specific functional IgG responses appear to be independent of the number and quality of circulating carrier-specific CD4+ T cells after priming.

Development and use of a serum bactericidal assay using pooled human complement to assess responses to a meningococcal group A conjugate vaccine in African toddlers

A meningococcal group A polysaccharide (PS) conjugate vaccine (PsA-TT) has been developed for African countries affected by epidemic meningitis caused by Neisseria meningitidis. Complement-mediated serum bactericidal antibody (SBA) assays are used to assess protective immune responses to meningococcal vaccination. Human complement (hC') was used in early studies demonstrating antibody-mediated protection against disease, but it is difficult to obtain and standardize. We developed and evaluated a method for sourcing hC' and then used the SBA assay with hC' (hSBA) to measure bactericidal responses to PsA-TT vaccination in 12- to 23-month-old African children. Sera with active complement from 100 unvaccinated blood donors were tested for intrinsic bactericidal activity, SBA titer using rabbit complement (rSBA), and anti-group A PS antibody concentration. Performance criteria and pooling strategies were examined and then verified by comparisons of three independently prepared hC' lots in two laboratories. hSBA titers of clinical trial sera were then determined using this complement sourcing method. Two different functional antibody tests were necessary for screening hC'. hSBA titers determined using three independent lots of pooled hC' were within expected assay variation among lots and between laboratories. In African toddlers, PsA-TT elicited higher hSBA titers than meningococcal polysaccharide or Hib vaccines. PsA-TT immunization or PS challenge of PsA-TT-primed subjects resulted in vigorous hSBA memory responses, and titers persisted in boosted groups for over a year. Quantifying SBA using pooled hC' is feasible and showed that PsA-TT was highly immunogenic in African toddlers.

Effectiveness of meningococcal serogroup C vaccine programmes

Since the introduction of monovalent meningococcal serogroup C (MenC) glycoconjugate (MCC) vaccines and the implementation of national vaccination programmes, the incidence of MenC disease has declined markedly as a result of effective short-term vaccination and reduction in acquisition of MenC carriage leading to herd protection. Monovalent and quadrivalent conjugate vaccines are commonly used vaccines to provide protection against MenC disease worldwide. Studies have demonstrated that MCC vaccination confers protection in infancy (0-12 months) from the first dose but this is only short-term. NeisVac-C(®) has the greatest longevity of the currently licensed MCC vaccines in terms of antibody persistence, however antibody levels have been found to fall rapidly after early infant vaccination with two doses of all MCC vaccines - necessitating a booster at ∼12 months. In toddlers, only one dose of the MCC vaccine is required for routine immunization. If herd protection wanes following catch-up campaigns, many children may become vulnerable to infection. This has led many to question whether an adolescent booster is also required.

The current situation of meningococcal disease in Latin America and recommendations for a new case definition from the Global Meningococcal Initiative

The Global Meningococcal Initiative (GMI) is an international group of scientists and clinicians with expertise in meningococcal disease (MD). It promotes MD prevention through education and research. Given geographic differences in disease epidemiology, prevention strategies (e.g., vaccination) should be country-specific to ensure local needs are met. However, regional policies/recommendations and standardized disease diagnostic criteria should be implemented to improve surveillance and control strategies, and allow for more robust data comparisons. Consequently, the GMI convened a meeting with Latin American representatives to discuss the burden of MD and vaccination practices/policies, and consider if the global GMI recommendations could be tailored. The group determined that as robust, uniform epidemiologic data are required to make informed health-policy decisions, it would be useful to first summarize the regional situation herein (including disease surveillance, case definitions, epidemiology, vaccination and outbreak control strategies) and then determine a consensus-based meningococcal case definition for use throughout the region.

Polysaccharide-protein conjugate vaccination induces antibody production but not sustained B-cell memory in the human nasopharyngeal mucosa

Colonization of the nasopharyngeal mucosa by meningococcus and other polysaccharide (PS)-encapsulated bacteria precedes invasion. PS-conjugate vaccines induce PS-specific B-cell memory (B(MEM)) and also prevent colonization, thus blocking person-to-person transmission, generating herd protection. However, in isolation the B(MEM) are unable to sustain immunity. Furthermore, the duration of herd protection the vaccines induce appears limited. We demonstrate that, despite the persistence of PS-specific B(MEM), the population is not maintained within the nasopharynx. Although booster immunization results in the transient appearance of PS-specific B(MEM) within the mucosa, this reflects the re-circulation of systemic B(MEM) through the site rather than the generation of resident mucosal B(MEM). The induction of sustained PS-specific B(MEM) in the nasopharynx would allow the population to be activated by colonization, thus inhibiting subsequent invasion. It would also be expected to boost local mucosal immunity, thus extending herd protection. Strategies to generate PS-specific B(MEM) in the mucosa warrant further investigation.

Three-year antibody persistence and safety after a single dose of combined haemophilus influenzae type b (Hib)-Neisseria meningitidis serogroup C-tetanus toxoid conjugate vaccine in Hib-primed toddlers

BACKGROUND

Persistence of seroprotective bactericidal antibody titers is important for long-term protection against meningococcal serogroup C disease in young children. Antibody persistence values were determined in children up to 3 years after vaccination with a single dose of the combined Haemophilus influenzae type b (Hib)-Neisseria meningitidis serogroup C (MenC)-tetanus toxoid (TT) conjugate vaccine (Hib-MenC-TT; www.ClinicalTrials.gov: NCT00326118).

METHODS

The children had been randomized at ages 12-18 months to receive either 1 dose of Hib-MenC-TT (Hib-MenC group) or separately administered Hib-TT conjugate vaccine and MenC-CRM197 (MCC) vaccine (Hib plus MCC group). All children had been primed in infancy with a Hib vaccine. Antibodies against MenC were measured by a serum bactericidal assay using rabbit complement (rSBA-MenC) and antibodies against Hib polyribosylribitol phosphate were assessed by enzyme-linked immunosorbent assay.

RESULTS

The rSBA-MenC titers ≥1:8 were demonstrated 3 years after vaccination in 64.2% and 53.2% of participants in the Hib-MenC group and in the Hib plus MCC group, respectively. Antipolyribosylribitol phosphate concentrations ≥0.15 µg/mL persisted in >98% of participants in both groups. The rSBA-MenC geometric mean titers and antipolyribosylribitol phosphate geometric mean concentrations remained higher 3 years after vaccination than before vaccination. No serious adverse events assessed by the investigator as being related to vaccination were reported.

CONCLUSION

In this antibody persistence study of Hib-primed but MenC-naïve toddlers who received a single dose of Hib-MenC-TT, protective antibody levels against Hib and MenC were maintained in the majority of children 3 years after vaccination.