scholarly journals Optimization and Application of a Multiplex Bead-Based Assay To Quantify Serotype-Specific IgG against Streptococcus pneumoniae Polysaccharides: Response to the Booster Vaccine after Immunization with the Pneumococcal 7-Valent Conjugate Vaccine

2010 ◽  
Vol 17 (4) ◽  
pp. 674-682 ◽  
Author(s):  
Karin E. M. Elberse ◽  
Irina Tcherniaeva ◽  
Guy A. M. Berbers ◽  
Leo M. Schouls
Keyword(s):  
Conjugate Vaccine ◽  
Geometric Mean ◽  
Booster Vaccination ◽  
Cross Reactivity ◽  
Serum Samples ◽  
Primary Series ◽  
Reference Serum ◽  
Specific Igg ◽  
Protective Threshold ◽  
Multiplex Bead

ABSTRACT We describe the optimization and application of a multiplex bead-based assay (Luminex) to quantify antibodies against polysaccharides of 13 pneumococcal serotypes. In the optimized multiplex immunoassay (MIA), intravenous immune globulin was introduced as an in-house reference serum, and nonspecific reacting antibodies were adsorbed with the commercial product pneumococcal C polysaccharides Multi. The antibody concentrations were assessed in 188 serum samples obtained pre- and post-booster vaccination at 11 months after administration of a primary series of the pneumococcal seven-valent conjugate vaccine (PCV-7) at 2, 3, and 4 months of age. The results of the MIA were compared with those of the ELISA for the serotypes included in the seven-valent conjugated polysaccharide vaccine and for a non-vaccine serotype, serotype 6A. The geometric mean concentrations of the antibodies determined by MIA were slightly higher than those determined by ELISA. The correlations between the assays were good, with R 2 values ranging from 0.84 to 0.91 for all serotypes except serotype 19F, for which R 2 was 0.70. The concentrations of antibody against serotype 6A increased after the administration of PCV-7 due to cross-reactivity with serotype 6B. The differences between the results obtained by ELISA and MIA suggest that the internationally established protective threshold of 0.35 μg/ml should be reevaluated for use in the MIA and may need to be amended separately for each serotype.

scholarly journals Assignment of Weight-Based Antibody Units for Seven Additional Serotypes to a Human Pneumococcal Standard Reference Serum, 007sp

2015 ◽  
Vol 22 (11) ◽  
pp. 1154-1159 ◽  
Author(s):  
D. Goldblatt ◽  
C. Y. Tan ◽  
P. Burbidge ◽  
S. McElhiney ◽  
L. McLaughlin ◽  
...  
Keyword(s):  
Polysaccharide Vaccine ◽  
Enzyme Linked Immunosorbent Assay ◽  
Reference Standard ◽  
Concordance Correlation ◽  
Clinical Protocol ◽  
Serum Samples ◽  
Reference Serum ◽  
Specific Igg ◽  
Standard Serum ◽  
Adult Volunteers

ABSTRACTThe pneumococcal enzyme-linked immunosorbent assay (ELISA) reference standard serum, lot 89SF, has been in use since 1990 and was replaced in 2013 with a new reference standard, 007sp, that is projected to be available for the next 25 years. 007sp was generated under an FDA-approved clinical protocol; 278 adult volunteers were immunized with the 23-valent unconjugated polysaccharide vaccine Pneumovax II, and a unit of blood was obtained twice from each immunized subject within 120 days following immunization. Pooled serum was prepared from the plasma of 262 subjects, filled at 6 ml per vial, and lyophilized. Five independent laboratories participated in bridging the serotype-specific IgG assignments for 89SF to the new reference standard, 007sp, to establish equivalent reference values for 13 pneumococcal capsular serotypes (1,3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F) by using the WHO reference ELISA. In a second study involving three laboratories, a similar protocol was used to assign weight-based IgG concentrations in micrograms per ml to 007sp of seven serotypes (8, 10A, 11A, 12F, 15B, 22F, and 33F) also present in the 23-valent pneumococcal unconjugated polysaccharide vaccine. In addition, the IgG assignments for a 12-member WHO quality control (QC) serum panel were also extended to cover these seven serotypes. Agreement was excellent, with a concordance correlation coefficient (rc) of >0.996 when each laboratory was compared to the assigned values for the 12 WHO QC serum samples. There are four remaining pneumococcal serotypes (2, 9N, 17F, and 20) found in Pneumovax II for which IgG assignments exist for 89SF and remain to be bridged.

scholarly journals Quadrivalent Meningococcal Vaccination of Adults: Phase III Comparison of an Investigational Conjugate Vaccine, MenACWY-CRM, with the Licensed Vaccine, Menactra

2009 ◽  
Vol 16 (12) ◽  
pp. 1810-1815 ◽  
Author(s):  
Keith S. Reisinger ◽  
Roger Baxter ◽  
Stanley L. Block ◽  
Jina Shah ◽  
Lisa Bedell ◽  
...  
Keyword(s):  
Single Dose ◽  
Conjugate Vaccine ◽  
Geometric Mean ◽  
Case Fatality ◽  
The United States ◽  
Phase Iii ◽  
Serum Samples ◽  
Serious Adverse Event ◽  
Specific Serum ◽  
To Receive

ABSTRACT Neisseria meningitidis is a leading cause of bacterial meningitis in the United States, with the highest case fatality rates reported for individuals ≥15 years of age. This study compares the safety and immunogenicity of the Novartis Vaccines investigational quadrivalent meningococcal CRM197 conjugate vaccine, MenACWY-CRM, to those of the licensed meningococcal conjugate vaccine, Menactra, when administered to healthy adults. In this phase III multicenter study, 1,359 adults 19 to 55 years of age were randomly assigned to one of four groups (1:1:1:1 ratio) to receive a single dose of one of three lots of MenACWY-CRM or a single dose of Menactra. Serum samples obtained at baseline and 1 month postvaccination were tested for serogroup-specific serum bactericidal activity using human complement (hSBA). The hSBA titers following vaccination with MenACWY-CRM and Menactra were compared in noninferiority and prespecified superiority analyses. Reactogenicity was similar in the MenACWY-CRM and Menactra groups, and neither vaccine was associated with a serious adverse event. When compared with Menactra, MenACWY-CRM met the superiority criteria for the proportions of recipients achieving a seroresponse against serogroups C, W-135, and Y and the proportion of subjects achieving postvaccination titers of ≥1:8 for serogroups C and Y. MenACWY-CRM's immunogenicity was statistically noninferior (the lower limit of the two-sided 95% confidence interval was more than −10%) to that of Menactra for all four serogroups, with the postvaccination hSBA geometric mean titers being consistently higher for MenACWY-CRM than for Menactra. MenACWY-CRM is well tolerated in adults 19 to 55 years of age, with immune responses to each of the serogroups noninferior and, in some cases, statistically superior to those to Menactra.

scholarly journals Schedules for Pneumococcal Vaccination of Preterm Infants: An RCT

2018 ◽  
pp. 18-32
Author(s):  
Alison Kent ◽  
Shamez N. Ladhani ◽  
Nick J. Andrews ◽  
Tim Scorrer ◽  
Andrew J. Pollard ◽  
...  
Keyword(s):  
Preterm Infants ◽  
Conjugate Vaccine ◽  
Invasive Pneumococcal Disease ◽  
Premature Infants ◽  
Pneumococcal Conjugate Vaccine ◽  
Pneumococcal Disease ◽  
Geometric Mean ◽  
Pneumococcal Vaccination ◽  
Booster Vaccination ◽  
Vaccine Schedule

BACKGROUND AND OBJECTIVE Premature infants have a higher risk of invasive pneumococcal disease and are more likely to have lower vaccine responses compared with term infants. Increasingly, immunization schedules are including a reduced, 2-dose, pneumococcal conjugate vaccine priming schedule. Our goal was to assess the immunogenicity of 3 commonly used 13-valent pneumococcal conjugate vaccine (PCV13) priming schedules in premature infants and their response to a 12-month booster dose. METHODS Premature infants (<35 weeks’ gestation) were randomized to receive PCV13 at 2 and 4 months (reduced schedule); 2, 3, and 4 months (accelerated schedule); or 2, 4, and 6 months (extended schedule). All infants received a 12-month PCV13 booster. Serotype-specific pneumococcal immunoglobulin G (IgG) for PCV13 serotypes was measured by using enzyme-linked immunosorbent assay 1 month after the primary and booster vaccinations. RESULTS A total of 210 infants (median birth gestation, 29+6 weeks; range, 23+2–34+6 weeks) were included. After the primary vaccination, 75% (95% confidence interval [CI], 62–85), 88% (95% CI, 76–95), and 97% (95% CI, 87–99) of participants had protective antibody concentrations for at least one-half the PCV13 serotypes for the reduced, accelerated, and extended schedules, respectively. After the booster vaccination, participants receiving the extended schedule had significantly lower (P < .05) geometric mean concentrations compared with reduced (for 9 of 13 serotypes) and accelerated (for 4 of 13 serotypes) schedules, but nearly all participations, regardless of schedule or serotype, had seroprotective IgG concentrations. CONCLUSIONS A reduced priming schedule of PCV13 resulted in higher post-booster IgG concentrations but lower post-primary concentrations. The optimum vaccine schedule for preterm infants will therefore depend on when they are most at risk for invasive pneumococcal disease.

scholarly journals Investigation of Different Group A Immunoassays following One Dose of Meningococcal Group A Conjugate Vaccine or A/C Polysaccharide Vaccine in Adults

2009 ◽  
Vol 16 (7) ◽  
pp. 969-977 ◽  
Author(s):  
H. Findlow ◽  
B. D. Plikaytis ◽  
A. Aase ◽  
M. C. Bash ◽  
H. Chadha ◽  
...  
Keyword(s):  
Conjugate Vaccine ◽  
Geometric Mean ◽  
Correlation Coefficients ◽  
Polysaccharide Vaccine ◽  
Enzyme Linked Immunosorbent Assay ◽  
Double Blind ◽  
Group A ◽  
Specific Igg ◽  
Immunologic Assays ◽  
The Relationship

ABSTRACT A double-blind, randomized, controlled phase I study to assess the safety, immunogenicity, and antibody persistence of a new group A conjugate vaccine (PsA-TT) in volunteers aged 18 to 35 years was previously performed. Subjects received one dose of either the PsA-TT conjugate vaccine, meningococcal A/C polysaccharide vaccine (PsA/C), or tetanus toxoid vaccine. The conjugate vaccine was shown to be safe and immunogenic as demonstrated by a standardized group A-specific immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) and by a serum bactericidal antibody (SBA) assay using rabbit complement (rSBA). This report details further analysis of the sera using four additional immunologic assays to investigate the relationship between the different immunoassays. The immunoassays used were an SBA assay that used human complement (hSBA), a group A-specific IgG multiplexed bead assay, and two opsonophagocytic antibody (OPA) assays which used two different methodologies. For each vaccine group, geometric mean concentrations or geometric mean titers were determined for all assays before and 4, 24, and 48 weeks after vaccination. Pearson's correlation coefficients were used to assess the relationship between the six assays using data from all available visits. An excellent correlation was observed between the group A-specific IgG concentrations obtained by ELISA and those obtained by the multiplexed bead assay. hSBA and rSBA titers correlated moderately, although proportions of subjects with putatively protective titers and those demonstrating a ≥4-fold rise were similar. The two OPA methods correlated weakly and achieved only a low correlation with the other immunoassays. The correlation between hSBA and group A-specific IgG was higher for the PsA-TT group than for the PsA/C group.

scholarly journals Effects of Alum Adjuvant or a Booster Dose on Immunogenicity during Clinical Trials of Group B Streptococcal Type III Conjugate Vaccines

2001 ◽  
Vol 69 (11) ◽  
pp. 6696-6701 ◽  
Author(s):  
L. C. Paoletti ◽  
M. A. Rench ◽  
D. L. Kasper ◽  
D. Molrine ◽  
D. Ambrosino ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Conjugate Vaccine ◽  
Capsular Polysaccharide ◽  
Phase 1 ◽  
Geometric Mean ◽  
Healthy Adults ◽  
Conjugate Vaccines ◽  
Type Iii ◽  
Specific Igg ◽  
Group B

ABSTRACT Phase 1 and 2 clinical trials of group B streptococcal (GBS) capsular polysaccharide (CPS)-protein conjugate vaccines in healthy adults have demonstrated their safety and improved immunogenicity compared with uncoupled CPSs. Two recent trials sought to determine (i) whether adsorption of conjugate vaccine to aluminum hydroxide would improve immunogenicity and (ii) whether the CPS-specific immunoglobulin G (IgG) response could be boosted by administration of a second dose. Adsorption of GBS type III CPS-tetanus toxoid (III-TT) conjugate vaccine to alum did not improve the immune response to a 12.5-μg dose in healthy adult recipients. Four weeks after vaccination, the geometric mean antibody concentrations (GMCs) for the 15 recipients of III-TT with or without alum were 3.3 and 3.6 μg/ml, respectively. In the second trial, 36 healthy adults vaccinated previously with GBS III-TT conjugate were given a second 12.5-μg dose 21 months later. At 4 weeks after the second dose, the GMCs of type III CPS-specific IgG were similar to those measured 4 weeks after the primary vaccination, suggesting a lack of a booster response. However, 8 (22%) of the 36 participants who had undetectable III CPS-specific IgG (<0.05 μg/ml) before the first dose of III-TT conjugate exhibited a booster response to the second dose, with a fourfold-greater GMC of type III CPS-specific IgG than after the initial immunization. These results suggest that prior natural exposure to type III GBS or a related antigen may be responsible for the brisk IgG response to CPS noted in most adults after vaccination. However, a second dose of GBS III-TT conjugate vaccine may be required for adults whose initial CPS-specific IgG concentrations are very low and would also restore the initial peak-specific III CPS-IgG in responders to previous vaccination.

scholarly journals Seroprevalence of Antibodies against Serogroup C Meningococci in England in the Postvaccination Era

2008 ◽  
Vol 15 (11) ◽  
pp. 1694-1698 ◽  
Author(s):  
Caroline L. Trotter ◽  
Ray Borrow ◽  
Jamie Findlow ◽  
Ann Holland ◽  
Sarah Frankland ◽  
...  
Keyword(s):  
Similar Pattern ◽  
Geometric Mean ◽  
Herd Immunity ◽  
Age Groups ◽  
Serum Samples ◽  
The United Kingdom ◽  
Specific Igg ◽  
Catch Up ◽  
Antibody Levels ◽  
Mean Concentration

ABSTRACT The United Kingdom introduced meningococcal serogroup C conjugate (MCC) vaccines in 1999, resulting in substantial declines in serogroup C disease and carriage. Here, we measured the age-specific prevalence of serum bactericidal antibodies (SBA) to Neisseria meningitidis serogroup C and immunoglobulin G (IgG) concentrations to serogroups A, C, W-135, and Y in 2,673 serum samples collected in England between 2000 and 2004. We compared the seroprevalence of SBA titers of ≥8 in the postvaccination era with results from an earlier prevaccination study conducted using the same methods. We found that the percentages of individuals with protective SBA titers were higher in 2000 to 2004 in all of the age groups targeted for MCC vaccination. In the postvaccine era, the prevalence of protective titers was high (75%) in children who had recently been offered routine immunization, but this fell to 36% more than 18 months after scheduled immunization. In the cohorts targeted in the catch-up campaign, the percentage achieving SBA titers of ≥8 was higher in children offered the vaccine at ages 5 to 17 years than in children offered the vaccine at ages 1 to 4 years. The geometric mean concentration (GMC) IgG for serogroup C followed a similar pattern, corresponding to the age at and time since scheduled MCC vaccination. Serogroup-specific IgG GMCs for W-135 and Y were low and showed little variation by age. Serogroup A IgG GMCs were higher, possibly reflecting exposure to cross-reacting antigens. Although the incidence of serogroup C disease remains low due to persisting herd effects, population antibody levels to serogroup C meningococci should be monitored so that potentially susceptible age groups can be identified should herd immunity wane.

scholarly journals Evaluation of De-O-Acetylated Meningococcal C Polysaccharide-Tetanus Toxoid Conjugate Vaccine in Infancy: Reactogenicity, Immunogenicity, Immunologic Priming, and Bactericidal Activity against O-Acetylated and De-O-Acetylated Serogroup C Strains

2001 ◽  
Vol 69 (4) ◽  
pp. 2378-2382 ◽  
Author(s):  
Peter Richmond ◽  
Ray Borrow ◽  
Jamie Findlow ◽  
Sarah Martin ◽  
Carol Thornton ◽  
...  
Keyword(s):  
Tetanus Toxoid ◽  
Vaccine Development ◽  
Geometric Mean ◽  
Booster Vaccination ◽  
Immunologic Memory ◽  
Primary Series ◽  
Fourth Dose ◽  
Polio Immunization ◽  
Bactericidal Activities ◽  
Antibody Levels

ABSTRACT The polysaccharide capsule of serogroup C Neisseria meningitidis (MenC) has been integral to vaccine development. Licensed MenC vaccines contain the O-acetylated (OAc+) form of polysaccharide. Some MenC strains have de-O-acetylated (OAc−) polysaccharide, which may affect antibody specificity and functional activity when used in a vaccine. We evaluated an OAc-MenC conjugate-tetanus toxoid conjugate (MCC-TT) vaccine given concomitantly with whole-cell diphtheria-tetanus-pertussis, Haemophilus influenzae type b, and oral polio immunization in 83 infants at 2, 3, and 4 months of age. Serum bactericidal activities (SBA) against OAc+ and OAc− MenC strains and OAc+ and OAc− polysaccharide-specific immunoglobulin G (IgG) levels were evaluated. MCC-TT vaccine was well tolerated. All infants produced SBA titers of ≥8 after a single dose at 2 months of age. The SBA geometric mean titer for OAc+ strain C11 increased from 2.7 (95% confidence interval [CI] 2.2 to 3.2) to 320 (95% CI, 237 to 432), 773 (95% CI, 609 to 982), and 1,063 (95% CI, 856 to 1319) after one, two, and three doses of MCC-TT, respectively. OAc− IgG levels were twice as high as OAc+ IgG levels after the primary series of MCC-TT vaccine, and the SBA was significantly higher against the OAc− MenC strain. Antibody responses to booster vaccination with either OAc+ MenC polysaccharide vaccine (MACP) or a fourth dose of MCC-TT at 14 months of age provided evidence of immunologic memory. The acetylation status of the booster vaccine influenced the specificity of the response, with significantly higher OAc− IgG levels and SBA after MCC-TT vaccine compared to MACP vaccine but similar OAc+ antibody levels. MCC-TT vaccine is highly immunogenic and primes for immunologic memory against OAc+ and OAc− MenC strains in infancy.

scholarly journals Prevalence of Serum Bactericidal Antibody to Serogroup C Neisseria meningitidis in England a Decade after Vaccine Introduction

2012 ◽  
Vol 19 (8) ◽  
pp. 1126-1130 ◽  
Author(s):  
David A. Ishola ◽  
Ray Borrow ◽  
Helen Findlow ◽  
Jamie Findlow ◽  
Caroline Trotter ◽  
...  
Keyword(s):  
Disease Incidence ◽  
Geometric Mean ◽  
Booster Vaccination ◽  
Serum Samples ◽  
Vaccine Introduction ◽  
Population Immunity ◽  
Bactericidal Antibody ◽  
Catch Up ◽  
Antibody Levels ◽  
Conjugate Vaccination

ABSTRACTSerogroup C meningococcal disease incidence and carriage declined rapidly in the United Kingdom after infant serogroup C conjugate vaccination was introduced in 1999, with catch-up vaccination for children under 18 years. Antibody levels and effectiveness waned quickly in children vaccinated at 2, 3, and 4 months of age. Therefore, in 2006, the current revised schedule of doses at 3, 4, and 12 months was introduced. This study assessed age-specific protection in 2009 compared with data from historical prevaccination and early postvaccination studies. Rabbit complement serum bactericidal antibody (SBA) was measured in anonymously banked serum samples collected in England in 2009 (n= 1,174), taking titers of ≥8 as protective. Age-stratified proportions of SBA titers that were ≥8 and geometric mean titers were compared. SBA titers varied markedly by birth cohort and time since vaccination. Overall, 35% of samples (95% confidence interval [CI], 33 to 38%) had titers that were ≥8. Only in cohorts eligible for catch-up vaccination did the majority of individuals have protective antibody levels. Antibody levels were higher in children eligible for vaccination at primary and secondary school ages, compared to those eligible below the age of 5 years. In those eligible for completed vaccination under the current schedule, protective levels were very modest and there was no evidence of superiority to cohorts that were eligible for the previous schedule. This supports a need for older childhood or adolescent booster vaccination in those previously eligible for vaccination during the infant, toddler, or preschool periods, to maintain direct protection and potentially enhance population immunity.

scholarly journals Induction of Protective Serum Meningococcal Bactericidal and Diphtheria-Neutralizing Antibodies and Mucosal Immunoglobulin A in Volunteers by Nasal Insufflations of the Neisseria meningitidis Serogroup C Polysaccharide-CRM197 Conjugate Vaccine Mixed with Chitosan

2005 ◽  
Vol 73 (12) ◽  
pp. 8256-8265 ◽  
Author(s):  
Zhiming Huo ◽  
Ruchi Sinha ◽  
Edel A. McNeela ◽  
Ray Borrow ◽  
Rafaela Giemza ◽  
...  
Keyword(s):  
Neisseria Meningitidis ◽  
Conjugate Vaccine ◽  
Neutralizing Antibodies ◽  
Intramuscular Injection ◽  
Geometric Mean ◽  
Immunoglobulin A ◽  
Secretory Iga ◽  
Bactericidal Antibody ◽  
Specific Igg ◽  
Nasal Immunization

ABSTRACT Thirty-six healthy volunteers received either a single intramuscular injection of Neisseria meningitidis serogroup C polysaccharide (MCP)-CRM197 conjugate vaccine in alum or two nasal insufflations 28 days apart of the same vaccine powder, without alum, mixed with chitosan. Nasal immunization was well tolerated, with fewer symptoms reported than after intramuscular injection. The geometric mean concentrations of MCP-specific immunoglobulin G (IgG) after one nasal immunization were 3.25 μg/ml in naïve subjects and 14.4 μg/ml in subjects previously immunized parenterally, compared with 4.30 μg/ml in naïve subjects immunized intramuscularly. The geometric mean titer of serum bactericidal antibody (SBA) rose 24-fold after two nasal immunizations in naïve subjects and was comparable to parenteral immunization (1,080 versus 1,625). All subjects achieved SBA titers associated with protection after two nasal immunizations: even those with titers of <8 at entry. A single nasal immunization boosted the SBA titer to ≥128 in 96% of previously immunized subjects, and two immunizations achieved this level in 92% of naive subjects. MCP-specific IgG levels were ∼70% IgG2 and ∼20% IgG1 after nasal or intramuscular immunization. Increases in CRM197-specific IgG and diphtheria toxin-neutralizing activity were observed after nasal or intramuscular immunization, with balanced IgG1/IgG2 and higher IgG4. Significant MCP-specific secretory IgA was detected in nasal wash only after nasal immunization and predominantly on the immunized side. Simple nasal insufflation of existing MCP-CRM197 conjugate vaccines in chitosan offers an inexpensive but effective needle-free prime and boost against serogroup C N. meningitidis and diphtheria.

scholarly journals Immunogenicity and Safety of a Meningococcal Quadrivalent Conjugate Vaccine in Saudi Arabian Adolescents Previously Vaccinated with One Dose of Bivalent and Quadrivalent Meningococcal Polysaccharide Vaccines: a Phase III, Controlled, Randomized, and Modified Blind-Observer Study

2012 ◽  
Vol 19 (7) ◽  
pp. 999-1004 ◽  
Author(s):  
Yagob Al-Mazrou ◽  
Mohamed Khalil ◽  
Helen Findlow ◽  
Helen Chadha ◽  
Valerie Bosch Castells ◽  
...  
Keyword(s):  
Conjugate Vaccine ◽  
Geometric Mean ◽  
Saudi Arabian ◽  
Polysaccharide Vaccine ◽  
Exposed Group ◽  
Phase Iii ◽  
Rabbit Serum ◽  
Serum Samples ◽  
Naive Group ◽  
Bactericidal Antibody

ABSTRACTReduced immune responses to repeated polysaccharide vaccination have been previously reported, but there are limited immunogenicity data on the use of meningococcal polysaccharide vaccine (PSV) followed by meningococcal conjugate vaccine. Saudi Arabian adolescents (aged 16 to 19 years) who had previously been vaccinated with ≥1 dose of bivalent meningococcal polysaccharide vaccine and 1 dose of quadrivalent meningococcal polysaccharide (MPSV4) were enrolled in a controlled, randomized, and modified observer-blind study (collectively termed the PSV-exposed group). The PSV-exposed group was randomized to receive either quadrivalent meningococcal conjugate vaccine (MCV4) (n= 145 PSV-exposed/MCV4 group) or MPSV4 (n= 142 PSV-exposed/MPSV4 group), and a PSV-naïve group received MCV4 (n= 163). Serum samples collected prevaccination and 28 days postvaccination were measured by baby rabbit serum bactericidal antibody (rSBA) assay, and vaccine tolerability and safety were also evaluated. For each serogroup, the postvaccination geometric mean titers (GMTs) were significantly higher in the PSV-naïve group than in either group comprised of the PSV-exposed participants. The postvaccination serogroup C rSBA GMT was significantly higher in the PSV-MCV4 group than in the PSV-MPSV4 group after adjusting for prevaccination GMTs. Although not statistically significant, similar differences were observed for serogroups A, Y, and W-135. No worrisome safety signals were detected. This study demonstrated MCV4 to be safe and immunogenic in those who had previously received polysaccharide vaccination, and it suggests that conjugate vaccine can partially compensate for the hyporesponsiveness seen with repeated doses of polysaccharide vaccine.

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