Meningococcal ACWYX Conjugate Vaccine in 2-to-29-Year-Olds in Mali and Gambia

BACKGROUND

An effective, affordable, multivalent meningococcal conjugate vaccine is needed to prevent epidemic meningitis in the African meningitis belt. Data on the safety and immunogenicity of NmCV-5, a pentavalent vaccine targeting the A, C, W, Y, and X serogroups, have been limited.

METHODS

We conducted a phase 3, noninferiority trial involving healthy 2-to-29-year-olds in Mali and Gambia. Participants were randomly assigned in a 2:1 ratio to receive a single intramuscular dose of NmCV-5 or the quadrivalent vaccine MenACWY-D. Immunogenicity was assessed at day 28. The noninferiority of NmCV-5 to MenACWY-D was assessed on the basis of the difference in the percentage of participants with a seroresponse (defined as prespecified changes in titer; margin, lower limit of the 96% confidence interval [CI] above -10 percentage points) or geometric mean titer (GMT) ratios (margin, lower limit of the 98.98% CI >0.5). Serogroup X responses in the NmCV-5 group were compared with the lowest response among the MenACWY-D serogroups. Safety was also assessed.

RESULTS

A total of 1800 participants received NmCV-5 or MenACWY-D. In the NmCV-5 group, the percentage of participants with a seroresponse ranged from 70.5% (95% CI, 67.8 to 73.2) for serogroup A to 98.5% (95% CI, 97.6 to 99.2) for serogroup W; the percentage with a serogroup X response was 97.2% (95% CI, 96.0 to 98.1). The overall difference between the two vaccines in seroresponse for the four shared serogroups ranged from 1.2 percentage points (96% CI, -0.3 to 3.1) for serogroup W to 20.5 percentage points (96% CI, 15.4 to 25.6) for serogroup A. The overall GMT ratios for the four shared serogroups ranged from 1.7 (98.98% CI, 1.5 to 1.9) for serogroup A to 2.8 (98.98% CI, 2.3 to 3.5) for serogroup C. The serogroup X component of the NmCV-5 vaccine generated seroresponses and GMTs that met the prespecified noninferiority criteria. The incidence of systemic adverse events was similar in the two groups (11.1% in the NmCV-5 group and 9.2% in the MenACWY-D group).

CONCLUSIONS

For all four serotypes in common with the MenACWY-D vaccine, the NmCV-5 vaccine elicited immune responses that were noninferior to those elicited by the MenACWY-D vaccine. NmCV-5 also elicited immune responses to serogroup X. No safety concerns were evident. (Funded by the U.K. Foreign, Commonwealth, and Development Office and others; ClinicalTrials.gov number, NCT03964012.).

Meningococcal Serogroup ACWYX Conjugate Vaccine in Malian Toddlers

BACKGROUND

Neisseria meningitidis serogroups A, B, C, W, X, and Y cause outbreaks of meningococcal disease. Quadrivalent conjugate vaccines targeting the A, C, W, and Y serogroups are available. A pentavalent vaccine that also includes serogroup X (NmCV-5) is under development.

METHODS

We conducted a phase 2, observer-blinded, randomized, controlled trial involving Malian children 12 to 16 months of age. Participants were assigned in a 2:2:1 ratio to receive nonadjuvanted NmCV-5, alum-adjuvanted NmCV-5, or the quadrivalent vaccine MenACWY-D, administered intramuscularly in two doses 12 weeks apart. Participants were followed for safety for 169 days. Immunogenicity was assessed with an assay for serum bactericidal antibody (SBA) with rabbit complement on days 0, 28, 84, and 112.

RESULTS

A total of 376 participants underwent randomization, with 150 assigned to each NmCV-5 group and 76 to the MenACWY-D group; 362 participants received both doses of vaccine. A total of 1% of the participants in the nonadjuvanted NmCV-5 group, 1% of those in the adjuvanted NmCV-5 group, and 4% of those in the MenACWY-D group reported local solicited adverse events; 6%, 5%, and 7% of the participants, respectively, reported systemic solicited adverse events. An SBA titer of at least 128 was seen in 91 to 100% (for all five serotypes) of the participants in the NmCV-5 groups and in 36 to 99% (excluding serogroup X) of those in the MenACWY-D group at day 84 (before the second dose); the same threshold was met in 99 to 100% (for all five serotypes) of the participants in the NmCV-5 groups and in 92 to 100% (excluding serogroup X) of those in the MenACWY-D group at day 112. Immune responses to the nonadjuvanted and adjuvanted NmCV-5 formulations were similar.

CONCLUSIONS

No safety concerns were identified with two doses of NmCV-5. A single dose of NmCV-5 elicited immune responses that were similar to those observed with two doses of MenACWY-D. Adjuvanted NmCV-5 provided no discernible benefit over nonadjuvanted NmCV-5. (Funded by the U.K. Foreign, Commonwealth, and Development Office; ClinicalTrials.gov number, NCT03295318.).

Safety and immunogenicity of a pentavalent meningococcal conjugate vaccine containing serogroups A, C, Y, W, and X in healthy adults: a phase 1, single-centre, double-blind, randomised, controlled study

BACKGROUND

Invasive meningococcal disease is an important public health problem, especially in sub-Saharan Africa. After introduction of MenAfriVac in 2010, Neisseria meningitidis serogroup A disease has been almost eliminated from the region. However, serogroups C, W, Y, and X continue to cause disease outbreaks. We assessed the NmCV-5 pentavalent meningococcal conjugate vaccine targeting A, C, Y, W, and X serogroups in a first-in-man, phase 1 study.

METHODS

We did a single-centre, double-blind, randomised controlled trial at a research clinic in Baltimore (MD, USA). Participants were healthy adults aged 18-45 years with no history of meningococcal vaccination or previous meningococcal infection. We randomly assigned participants (1:1:1) by an SAS-generated random schedule to a single, 0·5 mL, intramuscular injection of aluminium-phosphate adjuvanted NmCV-5, non-adjuvanted NmCV-5, or control (the quadrivalent meningococcal conjugate vaccine Menactra). The randomisation sequence used a permuted block design with randomly chosen block sizes of three and six. The vaccines were prepared, labelled, and administered with procedures to ensure participants and study personnel remained masked to treatment. After vaccination, participants were observed in the clinic for 60 min for adverse reactions. Participants recorded daily temperature and injection site or systemic reactions at home and returned to the clinic for follow-up visits on days 7, 28, and 84 for safety assessments; blood samples were also collected on day 7 for safety laboratory assessment. A phone call contact was made 6 months after vaccination. Serum was collected before vaccination and 28 days after vaccination for immunological assessment with a rabbit complement-dependent serum bactericidal antibody (rSBA) assay. The primary objective was an intention-to-treat assessment of safety, measuring local and systemic reactogenicity over 7 days, unsolicited adverse events through 28 days, and serious adverse events over 6 months. The secondary objective for the assessment of immunogenicity, was a per-protocol analysis of rSBA before and 28 days after vaccination. This trial is registered with ClinicalTrials.gov, number NCT02810340.

FINDINGS

Between Aug 17, 2016, and Feb 16, 2017, we assigned 20 participants to each vaccine. All vaccines were well-tolerated. Pain was the most common local reaction, occurring in 12 (60%), ten (50%), and seven (35%) participants in the adjuvanted NmCV-5, non-adjuvanted NmCV-5, and control groups, respectively. Headache was the most common systemic reaction, occurring in five (25%), three (15%), and three (15%), respectively. Most solicited reactogenicity adverse reactions were mild (60 [74%] of 81) and all were self-limiting. None of the differences in proportions of individuals with each solicited reaction was significant (p>0·300 for all comparisons) between the three vaccination groups. There were no serious adverse events and 19 unsolicited non-serious adverse events in 14 (23%) participants. Both adjuvanted and non-adjuvanted NmCV-5 elicited high rSBA titres against all five meningococcal serogroups. The pre-vaccination geometric mean titres (GMTs) ranged from 3·36 to 53·80 for the control, from 6·28 to 187·00 for the adjuvanted vaccine, and from 4·29 to 350·00 for the non-adjuvanted vaccine, and the post-vaccination GMT ranged from 3·14 to 3214 for the control, from 1351 to 8192 for the adjuvanted vaccine, and from 1607 to 11 191 for the non-adjuvanted vaccine. Predicted seroprotective responses (ie, an increase in rSBA titres of eight times or more) for the adjuvanted and non-adjuvanted NmCV-5 were similar to control responses for all five serogroups.

INTERPRETATION

The adjuvanted and non-adjuvanted NmCV-5 vaccines were well tolerated and did not produce concerning adverse effects and resulted in immune responses that are predicted to confer protection against all five targeted serogroups of invasive meningococcal disease. Further clinical testing of NmCV-5 is ongoing, and additional clinical trials are necessary to confirm the safety and immunogenicity of NmCV-5 in target populations.

FUNDING

UK Department for International Development.

Antibody Persistence 1-5 Years Following Vaccination With MenAfriVac in African Children Vaccinated at 12-23 Months of Age

Background. Following mass vaccination campaigns in the African meningitis belt with group A meningococcal conjugate vaccine, MenAfriVac (PsA-TT), disease due to group A meningococci has nearly disappeared. Antibody persistence in healthy African toddlers was investigated.

Methods. African children vaccinated at 12–23 months of age with PsA-TT were followed for evaluation of antibody persistence up to 5 years after primary vaccination. Antibody persistence was evaluated by measuring group A serum bactericidal antibody (SBA) with rabbit complement and by a group A–specific IgG enzyme-linked immunosorbent assay (ELISA).

Results. Group A antibodies measured by SBA and ELISA were shown to decline in the year following vaccination and plateaued at levels significantly above baseline for up to 5 years following primary vaccination.

Conclusions. A single dose of PsA-TT induces long-term sustained levels of group A meningococcal antibodies for up to 5 years after vaccination.

Clinical Trials Registration. ISRTCN78147026.

Safety Monitoring in Group A Meningococcal Conjugate Vaccine Trials: Description, Challenges, and Lessons

BACKGROUND

The determination of the safety profile of any vaccine is critical to its widespread use in any population. In addition, the application of international guidelines to fit local context could be a challenging but important step toward obtaining quality safety data.

METHODS

In clinical studies of PsA-TT (MenAfriVac), safety was monitored immediately after vaccination, at 4-7 days for postimmunization local and systemic reactions, within 28 days for adverse events, and throughout the duration of study for serious adverse events. Initial and ongoing training of sites' staff were undertaken during the studies, and a data and safety monitoring board reviewed all the data during and after the studies.

RESULTS

The safety of PsA-TT was evaluated according to international standards despite obvious challenges in remote areas where these studies were conducted. These challenges included the need for uniformity of methods, timely reporting in the context of frequent communication problems, occurrence of seasonal diseases such as malaria and rotavirus diarrhea, and healthcare systems that required improvement.

CONCLUSIONS

The trials of PsA-TT highlighted the value of a robust vaccine development plan and design so that lessons learned in initial studies were incorporated into the subsequent ones, initial training and periodic retraining, strict monitoring of all procedures, and continuous channel of communication with all stakeholders that enabled the application of international requirements to local settings, with high quality of data.

Antibody Persistence at 1 and 4 Years Following a Single Dose of MenAfriVac or Quadrivalent Polysaccharide Vaccine in Healthy Subjects Aged 2-29 Years

BACKGROUND

Mass vaccination campaigns of the population aged 1-29 years with 1 dose of group A meningococcal (MenA) conjugate vaccine (PsA-TT, MenAfriVac) in African meningitis belt countries has resulted in the near-disappearance of MenA. The vaccine was tested in clinical trials in Africa and in India and found to be safe and highly immunogenic compared with the group A component of the licensed quadrivalent polysaccharide vaccine (PsACWY). Antibody persistence in Africa and in India was investigated.

METHODS

A total of 900 subjects aged 2-29 years were followed up for 4 years in Senegal, Mali, and The Gambia (study A). A total of 340 subjects aged 2-10 years were followed up for 1 year in India (study B). In study A, subjects were randomized in a 2:1 ratio, and in study B a 1:1 ratio to receive either PsA-TT or PsACWY. Immunogenicity was evaluated by measuring MenA serum bactericidal antibody (SBA) with rabbit complement and by a group A-specific immunoglobulin G (IgG) enzyme-linked immunosorbent assay.

RESULTS

In both studies, substantial SBA decay was observed at 6 months postvaccination in both vaccine groups, although more marked in the PsACWY group. At 1 year and 4 years (only for study A) postvaccination, SBA titers were relatively sustained in the PsA-TT group, whereas a slight increasing trend, more pronounced among the youngest, was observed in the participants aged <18 years in the PsACWY groups. The SBA titers were significantly higher in the PsA-TT group than in the PsACWY group at any time point, and the majority of subjects in the PsA-TT group had SBA titers ≥128 and group A-specific IgG concentrations ≥2 µg/mL at any point in time in both the African and Indian study populations.

CONCLUSIONS

Four years after vaccination with a single dose of PsA-TT vaccine in Africa, most subjects are considered protected from MenA disease.

CLINICAL TRIALS REGISTRATION

PsA-TT-003 (ISRCTN87739946); PsA-TT-003a (ISRCTN46335400).

A Phase 3, Double-Blind, Randomized, Active Controlled Study to Evaluate the Safety of MenAfriVac in Healthy Malians

Background. A safe, affordable, and highly immunogenic meningococcal A conjugate vaccine (PsA-TT, MenAfriVac) was developed to control epidemic group A meningitis in Africa. Documentation of the safety specifications of the PsA-TT vaccine was warranted, with sufficient exposure to detect potential rare vaccine-related adverse reactions.

Methods. This phase 3, double-blind, randomized, active controlled clinical study was designed to evaluate the safety—primarily vaccine-related serious adverse events (SAEs)—up to 3 months after administration of a single dose of the PsA-TT vaccine to subjects aged 1–29 years in Mali. Safety outcomes were also compared to those following a single dose of a licensed meningococcal ACWY polysaccharide vaccine (PsACWY).

Results. No vaccine-related SAEs occurred during the 3 months of follow-up of 4004 subjects vaccinated with a single dose of PsA-TT. When compared to PsACWY (1996 subjects), tenderness at the injection site appeared to be more frequent in the PsA-TT group. However, rates of local induration, systemic reactions, adverse events (AEs), and SAEs were similar in both groups, and unsolicited AEs and SAEs were all unrelated to the study vaccines.

Conclusions. The study confirmed on a large scale the excellent safety profile of a single dose of PsA-TT when administered to its entire target population of 1–29 years of age.

Clinical Trials Registration. PACTR ATMR201003000191317.

Ethical Challenges and Lessons Learned During the Clinical Development of a Group A Meningococcal Conjugate Vaccine

BACKGROUND

The group A meningococcal vaccine (PsA-TT) clinical development plan included clinical trials in India and in the West African region between 2005 and 2013. During this period, the Meningitis Vaccine Project (MVP) accumulated substantial experience in the ethical conduct of research to the highest standards.

METHODS

Because of the public-private nature of the sponsorship of these trials and the extensive international collaboration with partners from a diverse setting of countries, the ethical review process was complex and required strategic, timely, and attentive communication to ensure the smooth review and approval for the clinical studies. Investigators and their site teams fostered strong community relationships prior to, during, and after the studies to ensure the involvement and the ownership of the research by the participating populations. As the clinical work proceeded, investigators and sponsors responded to specific questions of informed consent, pregnancy testing, healthcare, disease prevention, and posttrial access.

RESULTS

Key factors that led to success included (1) constant dialogue between partners to explore and answer all ethical questions; (2) alertness and preparedness for emerging ethical questions during the research and in the context of evolving international ethics standards; and (3) care to assure that approaches were acceptable in the diverse community contexts.

CONCLUSIONS

Many of the ethical issues encountered during the PsA-TT clinical development are familiar to groups conducting field trials in different cultural settings. The successful approaches used by the MVP clinical team offer useful examples of how these problems were resolved.

CLINICAL TRIALS REGISTRATION

ISRCTN17662153 (PsA-TT-001); ISRTCN78147026 (PsA-TT-002); ISRCTN87739946 (PsA-TT-003); ISRCTN46335400 (PsA-TT-003a); ISRCTN82484612 (PsA-TT-004); CTRI/2009/091/000368 (PsA-TT-005); PACTR ATMR2010030001913177 (PsA-TT-006); PACTR201110000328305 (PsA-TT-007).

Conducting vaccine clinical trials in sub-Saharan Africa: operational challenges and lessons learned from the Meningitis Vaccine Project

Group A Neisseria meningitidis epidemics have been an important and unresolved public health problem in sub-Saharan Africa for over a century. The Meningitis Vaccine Project (MVP) was established in 2001 with the goal of developing, testing, licensing, and introducing an affordable group A meningococcal conjugate vaccine for Africa. A monovalent group A conjugate vaccine, MenAfriVac™, was developed at the Serum Institute of India Ltd. and tested in clinical trials at multiple trial sites in sub-Saharan African countries. The setup and successful conduct of ICH-GCP standard vaccine trials across multiple trial sites located in low-resource settings are challenging. We describe the main operational issues encountered in three randomized, observer-blind, active controlled studies to evaluate the safety and immunogenicity of MenAfriVac™. The studies were conducted in parallel among 2700 subjects aged between 2 months and 29 years of age enrolled across four trial sites located in Mali, The Gambia, Senegal, and Ghana between September 2006 and August 2009. Many important lessons were learned during the preparation, setup, and implementation of the Meningitis Vaccine Project clinical program. They are summarized here to help vaccine development programs identify efficient pathways for successful implementation of clinical trials in low-resource settings.

Immunogenicity and safety of a meningococcal A conjugate vaccine in Africans

BACKGROUND

Group A meningococci are the source of major epidemics of meningitis in Africa. An affordable, highly immunogenic meningococcal A conjugate vaccine is needed.

METHODS

We conducted two studies in Africa to evaluate a new MenA conjugate vaccine (PsA-TT). In study A, 601 children, 12 to 23 months of age, were randomly assigned to receive PsA-TT, a quadrivalent polysaccharide reference vaccine (PsACWY), or a control vaccine (Haemophilus influenzae type b conjugate vaccine [Hib-TT]). Ten months later, these children underwent another round of randomization within each group to receive a full dose of PsA-TT, a one-fifth dose of PsACWY, or a full dose of Hib-TT, with 589 of the original participants receiving a booster dose. In study B, 900 subjects between 2 and 29 years of age were randomly assigned to receive PsA-TT or PsACWY. Safety and reactogenicity were evaluated, and immunogenicity was assessed by measuring the activity of group A serum bactericidal antibody (SBA) with rabbit complement and performing an IgG group A-specific enzyme-linked immunosorbent assay.

RESULTS

In study A, 96.0% of the subjects in the PsA-TT group and 63.7% of those in the PsACWY group had SBA titers that were at least four times as high as those at baseline; in study B, 78.2% of the subjects in the PsA-TT group and 46.2% of those in the PsACWY group had SBA titers that were at least four times as high as those at baseline. The geometric mean SBA titers in the PsA-TT groups in studies A and B were greater by factors of 16 and 3, respectively, than they were in the PsACWY groups (P<0.001). In study A, the PsA-TT group had higher antibody titers at week 40 than the PsACWY group and had obvious immunologic memory after receiving a polysaccharide booster vaccine. Safety profiles were similar across vaccine groups, although PsA-TT recipients were more likely than PsACWY recipients to have tenderness and induration at the vaccination site. Adverse events were consistent with age-specific morbidity in the study areas; no serious vaccine-related adverse events were reported.

CONCLUSIONS

The PsA-TT vaccine elicited a stronger response to group A antibody than the PsACWY vaccine. (Funded by the Meningitis Vaccine Project through a grant from the Bill and Melinda Gates Foundation; Controlled-Trials.com numbers, ISRCTN78147026 and ISRCTN87739946.).