Immunogenicity and reactogenicity of a group C meningococcal conjugate vaccine compared with a group A+C meningococcal polysaccharide vaccine in adolescents in a randomised observer-blind controlled trial

Infections associated with the use of eculizumab: recommendations for prevention and prophylaxis

PURPOSE OF REVIEW

Eculizumab inhibits complement effector functions and has significantly impacted the treatment of paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. However, the risks of potentially life-threatening infections, notably with Neisseria spp. in addition to its cost, are major challenges in clinical practice. In this review, we characterize and summarize the infectious complications reported with the use of eculizumab in the context of its typical and expanding indications.

RECENT FINDINGS

Use of eculizumab is rapidly extending to the fields of transplantation and neurology. Eculizumab has been primarily associated with an increased risk of meningococcal infections. Immunization against its commonest serotypes (ABCWY) is now possible with the advent of the meningococcal B vaccine. A combined ABCWY vaccine is underway. Preventive strategies against breakthrough Neisseria infections should also include chemoprophylaxis. Less is known about the association of eculizumab with other infections as recently reported. Surrogate markers of complement blockade, notably CH50, and eculizumab efficacy may help in the risk assessment of infection.

SUMMARY

Eculizumab has opened new horizons in the treatment of complement-mediated disorders. Prophylactic and immunization strategies against the risk of Nesseria spp. infections are sound and feasible. The use of eculizumab is expanding beyond complement-mediated diseases to transplantation and neurological disorders. Further research is needed to better define and stratify the risk of infection and prevention strategies in patients with the latter indications.

Safety and immune response after two-dose meningococcal C conjugate immunization in HIV-infected children and adolescents in Rio de Janeiro, Brazil

We aimed to evaluate immunogenicity and adverse events (AEs) after a booster dose of Meningococcal C conjugated (MCC) vaccine in HIV-infected children and adolescents, who had a previous low seroconversion rate after priming with MCC, at a reference HIV-care center in Rio de Janeiro.

METHODS

2-18 years old HIV-infected subjects with CD4+ T-lymphocyte cell (CD4) ≥15%, without active infection or antibiotic use, were enrolled to receive 2 doses of conjugated meningococcal C oligosaccharide-CRM197 12-18 months apart. All patients were evaluated before and 1-2 months after immunization for seroprotection [defined as human serum bactericidal activity (hSBA) titer ≥1:4]. AEs were assessed at 20 min, 3 and 7 days after each dose. Factors independently associated with seroprotection were studied.

RESULTS

156 subjects were enrolled and 137 received a booster MCC dose. 55% were female, and median age was 12 years. Eight-nine percent were receiving combined antiretroviral therapy (cART) at the booster visit (median duration of 7.7 years), 59.9% had undetectable viral load (VL) at baseline, and 56.2% at the booster visit. Seroprotection was achieved in 78.8% (108/137) subjects, with a significantly higher GMT than after the priming dose (p < 0.01). Mild AEs were experienced after a second MCC dose (38%). In logistic regression, undetectable viral load at entry [odds ratio (OR) = 7.1, 95% confidence interval (95%CI): 2.14-23.37], and probably higher CD4 percent at the booster immunization visit (OR): 1.1, 95%CI: 1.01-1.17 were associated with seroprotection after a booster dose of MCC.

CONCLUSION

A booster dose of MCC was safe and induced high seroprotection rate even 12-18 months after priming. MCC should be administered after maximum virologic suppression has been achieved. These results support the recommendation of 2-dose of MCC for primary immunization in HIV-infected children and adolescents with restored immune function.

Immunogenicity and safety of meningococcal C conjugate vaccine in children and adolescents infected and uninfected with HIV in Rio de Janeiro, Brazil

BACKGROUND

We aimed to evaluate the Meningococcal (Neisseria meningitidis) C conjugated (MCC) vaccine seroconversion and adverse events (AEs) in HIV-infected and HIV-uninfected children and adolescents in Rio de Janeiro, Brazil.

METHODS

HIV-infected or HIV-uninfected subjects, 2-18 years old, with CD4+ T-lymphocyte cell (CD4) percentage >15%, without active infection or antibiotic use, were enrolled. All patients were evaluated before and 1-2 months after immunization for seroconversion (defined as ≥4-fold titer increase in human serum bactericidal activity) and at 20 minutes, 3 and 7 days after immunization for AEs. Factors associated with seroconversion among HIV-infected group were studied.

RESULTS

Two hundred four subjects were enrolled: 154 HIV-infected and 50 HIV-uninfected. Median age was 12 years, and 53% were female. Among the HIV-infected group, 82 (53%) had a history of at least 1 C clinical category of Centers for Diseases Control and Prevention event, and 134 (87%) were using combination antiretroviral therapy. The median nadir CD4 percentage was 13% (0-47%). Seventy-six (37.3%) experienced mild AEs. Seroconversion occurred in 46 of 154 (30%) in the HIV-infected group and in 38 of 50 (76%) in the uninfected group (P < 0.01). Factors associated with seroconversion in the HIV-infected group were as follows: never had a C clinical category event [odds ratio (OR) = 2.1, 95% confidence interval (CI): 1.0-4.4]; undetectable viral load at immunization (OR: 2.4, 95% CI: 1.1-5.2) and higher CD4 nadir/100 cells (OR: 1.1, 95% CI: 1.0-1.2).

CONCLUSION

MCC vaccine should be administered to HIV-infected children and adolescents after maximum immunologic and virologic benefits have been achieved with combination antiretroviral therapy. Our data suggest that a single dose of MCC vaccine is insufficient for HIV-infected individuals 2-18 years of age.

Global practices of meningococcal vaccine use and impact on invasive disease

A number of countries now include meningococcal vaccines in their routine immunization programs. This review focuses on different approaches to including meningococcal vaccines in country programs across the world and their effect on the burden of invasive meningococcal disease (IMD) as reflected by pre and post-vaccine incidence rates in the last 20 years. Mass campaigns using conjugated meningococcal vaccines have lead to control of serogroup C meningococcal disease in the UK, Canada, Australia, Spain, Belgium, Ireland, and Iceland. Serogroup B disease, predominant in New Zealand, has been dramatically decreased, partly due to the introduction of an outer membrane vesicle (OMV) vaccine. Polysaccharide vaccines were used in high risk people in Saudi Arabia and Syria and in routine immunization in China and Egypt. The highest incidence region of the meningitis belt initiated vaccination with the serogroup A conjugate vaccine in 2010 and catch-up vaccination is ongoing. Overall results of this vaccine introduction are encouraging especially in countries with a moderate to high level of endemic disease. Continued surveillance is required to monitor effectiveness in countries that recently implemented these programs.

Meningococcal vaccines: current issues and future strategies

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

Control and lot release of meningococcal group C conjugate vaccines

Meningococcal group C conjugate vaccines were first introduced to the UK in 1999. To date, the vaccines have been demonstrated to have an efficacy of approximately 90% and have since been adopted by other countries worldwide. The development of control tests used for lot release of meningococcal group C vaccines has been based on those used for Haemophilus influenzae type b conjugates, the key criteria being measurement of free saccharide and conjugate integrity by physicochemical means. In future, meningococcal group C vaccines are likely to be replaced by multivalent formulations containing different components in combination. This will present a new challenge for regulatory authorities and more extensive testing will be required to ensure vaccine safety and efficacy.

Long-term protection in children with meningococcal C conjugate vaccination: lessons learned

Owing to an increase in group C disease, extensive prelicensure studies have been funded by both the UK Department of Health and vaccine manufacturers. These demonstrated the safety and immunogenicity of three candidate meningococcal group C conjugate (MCC) vaccines (two conjugated to CRM(197) and one to tetanus toxoid) in the targeted age groups. Induction of immunological memory in infants and young children was also demonstrated by either a low dose of polysaccharide challenge following primary immunization with MCC or by an increase in avidity indices post-primary to pre-challenge. Immune memory after infant immunization persisted to at least 4 years of age, although antibody persistence in this age group was poor. MCC vaccine was introduced into the UK routine immunization schedule at 2, 3 and 4 months of age in 1999, with a catch-up as a single dose to all children aged 1-18 years with two doses for infants aged 5-11 months. The number of group C cases fell rapidly in the targeted age groups and early analyzes showed high vaccine effectiveness in all age groups together with significant herd immunity. However, when effectiveness was measured again more than 1 year after vaccination, there was a significant decline in all age groups, most marked in infants vaccinated in the routine infant immunization program, for whom there was no demonstrable efficacy after only 1 year and then in toddlers for whom efficacy declined to 61% (95% confidence interval: -327-94) from 88% (95% confidence interval: 65-96) in the first year. However, good disease control was maintained in the UK with only low numbers of vaccine failures. The assumption that immune memory was predictive of long-term protection is incorrect, at least after vaccination in infancy. Persistence of antibody and herd immunity may be more relevant for long-term disease control.

Use and interpretation of diagnostic vaccination in primary immunodeficiency: a working group report of the Basic and Clinical Immunology Interest Section of the American Academy of Allergy, Asthma & Immunology

A major diagnostic intervention in the consideration of many patients suspected to have primary immunodeficiency diseases (PIDDs) is the application and interpretation of vaccination. Specifically, the antibody response to antigenic challenge with vaccines can provide substantive insight into the status of human immune function. There are numerous vaccines that are commonly used in healthy individuals, as well as others that are available for specialized applications. Both can potentially be used to facilitate consideration of PIDD. However, the application of vaccines and interpretation of antibody responses in this context are complex. These rely on consideration of numerous existing specific studies, interpolation of data from healthy populations, current diagnostic guidelines, and expert subspecialist practice. This document represents an attempt of a working group of the American Academy of Allergy, Asthma & Immunology to provide further guidance and synthesis in this use of vaccination for diagnostic purposes in consideration of PIDD, as well as to identify key areas for further research.

Immunogenicity of a meningococcal serogroup C conjugate vaccine in HIV-infected children, adolescents, and young adults

Children and adolescents infected with HIV typically have a lower response to immunization than do those in the general population. In most developed countries, meningococcal serogroup C conjugate vaccine is one of the recommended vaccines for such individuals. However, there have been no studies evaluating the antibody response to this vaccine in HIV-infected children, adolescents or young adults. In this study, we evaluated that response using serum bactericidal antibody (SBA) and enzyme-linked immunosorbent assay, comparing HIV-infected with non-HIV-infected patients, as well as analysing the occurrence of side effects. In non-responders, we assessed the antibody response to revaccination. This clinical trial involved 92 patients between 10 and 20 years of age: 43 HIV-infected patients (HIV+ group) and 49 non-HIV-infected patients (HIV- group). After one dose of the vaccine, 72.1% of the HIV+ group patients and 100% of the HIV- group patients were considered protected. Of the HIV+ group patients who received a second dose of the vaccine, only 40% acquired protection. Overall, 81.4% of the HIV+ group patients acquired protection (after one or two doses of the vaccine). Side effects occurred in 16.3% and 44% of the HIV+ group and HIV- group patients, respectively. Therefore, the meningococcal serogroup C conjugate vaccine proved to be safe and effective for use in HIV-infected children, adolescents, and young adults, although their antibody response was weaker than that shown by non-HIV-infected patients. This indicates the need to discuss changes to the immunization schedule for children, adolescents, and young adults infected with HIV, in order to ensure more effective protection against meningococcal disease.

Hyporesponsiveness following booster immunization with bacterial polysaccharides is caused by apoptosis of memory B cells

BACKGROUND

Repeated immunizations with polysaccharide (PS) vaccines cause hyporesponsiveness through undefined mechanisms. We assessed the effects of a PS booster on immune responses, frequency, and survival of PS-specific B-cell subpopulations in spleen and bone marrow.

METHODS

Neonatal mice were primed with meningococcus serotype C (MenC) conjugate MenC-CRM(197)+CpG1826, boosted with MenC-CRM(197), MenC-PS, or saline; subsequently, bromodeoxyuridine (BrdU) was injected daily intraperitoneally. MenC-PS-specific cells were labeled with fluorescent MenC-PS and phenotyped by flow cytometry.

RESULTS

After MenC-PS booster, proliferating (BrdU(+)) MenC-PS-specific naive B cells (CD138(-)/B220(+); P = .0003) and plasma cells (CD138(+)/B220(-); P = .0002) in spleen were fewer than after saline booster. BrdU(+) MenC-PS-specific plasma cells were also reduced in bone marrow (P = .0308). Compared to saline, MenC-PS booster reduced BrdU(+) IgG(+) MenC-PS-specific B cells in spleen (P = .0002). Twelve hours after the MenC-PS booster, an increased frequency of apoptotic (AnnexinV(+)) MenC-PS-specific B cells in spleen was observed compared with MenC-CRM(197) (P = .0286) or saline (P = .001) boosters.

CONCLUSIONS

We demonstrated that the MenC-PS booster significantly reduced the frequency of newly activated MenC-PS-specific B cells-mostly switched IgG(+) memory cells-by driving them into apoptosis. It shows directly that apoptosis of PS-specific memory cells is the cause of PS-induced hyporesponsiveness. These results should be taken into account prior to consideration of the use of PS vaccines.

Meningococcal conjugate vaccines: optimizing global impact

Meningococcal conjugate vaccines have several advantages over polysaccharide vaccines, including the ability to induce greater antibody persistence, avidity, immunologic memory, and herd immunity. Since 1999, meningococcal conjugate vaccine programs have been established across the globe. Many of these vaccination programs have resulted in significant decline in meningococcal disease in several countries. Recent introduction of serogroup A conjugate vaccine in Africa offers the potential to eliminate meningococcal disease as a public health problem in Africa. However, the duration of immune response and the development of widespread herd immunity in the population remain important questions for meningococcal vaccine programs. Because of the unique epidemiology of meningococcal disease around the world, the optimal vaccination strategy for long-term disease prevention will vary by country.

WITHDRAWN: Conjugate vaccines for preventing meningococcal C meningitis and septicaemia

BACKGROUND

Meningococcal polysaccharide (MPLS) vaccines protect against Serogroup C disease, but do not produce an immune response in infants less than two years of age. This limitation can be overcome by linking C polysaccharide to carrier proteins ('conjugating'), to create meningococcal serogroup C conjugate (MCC) vaccines. In the absence of trial data, the immune response to vaccination has been considered to be a reasonable surrogate for vaccine protection.

OBJECTIVES

To assess the immunogenicity, safety and efficacy of MCC vaccines for preventing meningitis and septicaemia.

SEARCH STRATEGY

We searched the Cochrane Central Register Controlled Trials (CENTRAL) (The Cochrane Library 2005, issue 3); MEDLINE (1966 to September, Week 1 2005); and EMBASE (1990 to June 2005) and references of studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and controlled clinical trials (CCTs) in humans comparing MCC vaccines against a control vaccine or none. In the absence of any trials on vaccine efficacy, population-based observational studies about effectiveness were included.

DATA COLLECTION AND ANALYSIS

Two authors independently screened the results of the literature searches, selected eligible studies, extracted the data and evaluated the quality of them.

MAIN RESULTS

The studies showed that MCC vaccine was highly immunogenic in infants after two and three doses, in toddlers after one and two doses and in older age groups after one dose. In general higher titres were generated after MCC than after MPLS vaccines. Immunological hypo-responsiveness seen after repeated doses of MPLS vaccine may be overcome with MCC. Observational studies have documented a significant decline in meningococcal C disease in countries where MCC vaccines have been widely used. The timing of the vaccinations schedules, the specific conjugate used, and the vaccines given concomitantly or combined, may be important.

AUTHORS' CONCLUSIONS

The MCC vaccine appears to be safe, immunogenic and able to induce immunological memory in all age groups. Observational studies strongly suggest that MCC is clinically effective.

Serum antibody kinetics following nasal or parenteral challenge with meningococcal polysaccharide in healthy adults

Limited data are available on the kinetics of meningococcal serogroup C (MenC)-specific antibody responses following parenteral or nasal challenge in those who have received prior MenC vaccination (polysaccharide or conjugate). Young adults who had previously received either meningococcal A/C polysaccharide (MACP) or MenC conjugate (MCC) vaccine or naïve subjects were challenged with MACP via one of two routes, nasal or parenteral. Blood samples were taken prevaccination and on days 1 to 4 and day 10 postvaccination. MenC serum bactericidal antibody (SBA) and MenC-specific IgG were measured. Following parenteral challenge, MenC SBA and IgG responses were seen to occur between 4 and 7 days postchallenge. A lower proportion of subjects responded following nasal challenge, with naïve subjects showing little change in SBA geometric mean titer (GMT) and IgG geometric mean concentration (GMC) over the 10 days following challenge. Increases in SBA GMTs were seen between 4 and 7 days after nasal challenge in those who had received prior MCC and between 7 and 10 days in those who had received prior MACP, and the responses in the prior-MACP group were of lower magnitude than the responses of the prior-MCC group. The data presented here indicate that, following MCC vaccination, memory has been induced at the mucosal level, and these subjects were able to respond with increases in SBA levels. These results demonstrate that the speed of response (primary or secondary) to challenge with MenC polysaccharide via the nasal or parenteral route does not differ and support concerns that immunological memory alone is too slow to provide protection.

The impact of childhood meningococcal serogroup C conjugate vaccine programs in Canada

BACKGROUND

Conjugate meningococcal vaccines may decrease the incidence of disease. The staggered implementation of universal childhood meningococcal C conjugate (MenC) immunization programs across Canada offers an opportunity to evaluate the influence of these programs.

METHODS

From 2002 to 2006, we conducted active, population-based surveillance for adult and pediatric hospital admissions related to meningococcal infections at the 12 centers of the Canadian Immunization Monitoring Program, Active (IMPACT), in collaboration with local public health officials.

RESULTS

A total of 376 cases were reported during the 5 years of surveillance. Yearly totals were as follows: 96 in 2002, 73 in 2003, 81 in 2004, 58 in 2005, and 68 in 2006. Case fatality was 9.3% and adults had a significantly higher case fatality rate than children.Average incidence per 100,000 was 0.62 (95% confidence interval [CI]: 0.50-0.76) in 2002 and 0.42 (95% CI: 0.32-0.53) in 2006. The highest rates were in children age 0 to 4 years, followed by adolescents age 15 to 19 years. Incidence of group C disease decreased significantly during the 5 years from 0.23 (95% CI: 0.16-0.32) in 2002 to 0.08 (95% CI: 0.04-0.14) in 2006, whereas incidence remained stable for groups B, Y, and W135. The decrease in group C disease was seen in provinces that first implemented MenC immunization programs.

CONCLUSIONS

A substantial decrease in group C incidence occurred in provinces with early MenC immunization programs. Serogroup C incidence remained stable in provinces without MenC programs. We found no evidence of serogroup replacement.

Two versus three doses of a meningococcal C conjugate vaccine concomitantly administered with a hexavalent DTaP-IPV-HBV/Hib vaccine in healthy infants

The immunogenicity and reactogenicity of a meningococcal serogroup C (MenC) conjugate vaccine given concomitantly with DTaP-IPV-HBV/Hib vaccine according to a two- or three-dose schedule in healthy infants was evaluated. At 1 month post-vaccination, 98% (two doses) and 100% (three doses) of subjects had serum bactericidal antibody using human complement assay (hSBA) titres > or =1:8; at 12 months of age > or =89% of subjects in each group remained seroprotected. Induction of immunological memory, as evaluated by administration of a meningococcal serogroup A/C polysaccharide vaccine challenge dose, was similar for both regimens and no interference was observed in the immune response to MenC or hepatitis B virus antigens. Reactogenicity was similar in each group. MenC conjugate vaccine given concomitantly with DTaP-IPV-HBV/Hib to healthy infants in the first year of life using a two-dose schedule is as safe and immunogenic as a three-dose regimen.

Reconsideration of the use of meningococcal polysaccharide vaccine

In 2005, a quadrivalent meningococcal conjugate vaccine was licensed in the United States for persons aged 11-55 years of age. For children aged 2-10 years with underlying diseases associated with increased risk of meningococcal disease, unconjugated meningococcal polysaccharide (MPS) vaccination is still recommended. This article reviews the increasing evidence that MPS vaccination impairs serum anticapsular antibody responses to subsequent injections of MPS or meningococcal conjugate vaccines (antibody hyporesponsiveness). Administering MPS as a probe to assess conjugate vaccine-induced immunologic memory also can extinguish subsequent memory anticapsular antibody responses, whereas conjugate vaccination regenerates memory B cells. Whether induction of antibody hyporesponsiveness or loss of immunologic memory increase the risk of acquiring meningococcal disease remains speculative. However, for children at increased risk of meningococcal disease, immunization with meningococcal quadrivalent conjugate vaccine off-label instead of MPS vaccine should be considered. Requirements for licensure of new glycoconjugate vaccines that include performing comparative clinical trials to demonstrate noninferiority with MPS vaccine, or use of a MPS challenge to assess conjugate-induced immunologic memory also should be modified because there are safer approaches for obtaining the same information.

Conjugate vaccines for preventing meningococcal C meningitis and septicaemia

BACKGROUND

Meningococcal polysaccharide (MPLS) vaccines protect against Serogroup C disease, but do not produce an immune response in infants less than two years of age. This limitation can be overcome by linking C polysaccharide to carrier proteins ('conjugating'), to create meningococcal serogroup C conjugate (MCC) vaccines. In the absence of trial data, the immune response to vaccination has been considered to be a reasonable surrogate for vaccine protection.

OBJECTIVES

To assess the immunogenicity, safety and efficacy of MCC vaccines for preventing meningitis and septicaemia.

SEARCH STRATEGY

We searched the Cochrane Central Register Controlled Trials (CENTRAL) (The Cochrane Library Issue 3, 2005); MEDLINE (1966 to September, Week 1 2005); and EMBASE (1990 to June 2005) and references of studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and controlled clinical trials (CCTs) in humans comparing MCC vaccines against a control vaccine or none. In the absence of any trials on vaccine efficacy, population-based observational studies about effectiveness were included.

DATA COLLECTION AND ANALYSIS

Two authors independently screened the results of the literature searches, selected eligible studies, extracted the data and evaluated the quality of them.

MAIN RESULTS

The studies showed that MCC vaccine was highly immunogenic in infants after two and three doses, in toddlers after one and two doses and in older age groups after one dose. In general higher titres were generated after MCC than after MPLS vaccines. Immunological hypo-responsiveness seen after repeated doses of MPLS vaccine may be overcome with MCC. Observational studies have documented a significant decline in meningococcal C disease in countries where MCC vaccines have been widely used. The timing of the vaccinations schedules, the specific conjugate used, and the vaccines given concomitantly or combined, may be important.

AUTHORS' CONCLUSIONS

The MCC vaccine appears to be safe, immunogenic and able to induce immunological memory in all age groups. Observational studies strongly suggest that MCC is clinically effective.

Meningococcal polysaccharide-protein conjugate vaccines

It is now 5 years since the UK became the first country to introduce the serogroup C meningococcal polysaccharide-protein conjugate vaccines (MenC) into its routine immunisation schedule. This article reviews the global use of MenC with particular reference to the range of immunisation strategies used internationally. To date, concerns that MenC may result in an increase in meningococcal disease due to non-C serogroups have not been realised. The vaccine has proved to be highly safe and effective; however, concerns have arisen regarding the duration of vaccine effectiveness. Although booster doses of MenC may potentially extend the duration of protection offered by the vaccine, there are, as yet, no studies assessing this option. Clinical trials are underway to assess new combination conjugate vaccines (containing A, C, Y, and W polysaccharides), and it is probable that these more broadly protective vaccines will become available in the near future.

Meningococcal vaccines

Meningococcal disease is one of the most feared and serious infections in the young and its prevention by vaccination is an important goal. The high degree of antigenic variability of the organism makes the meningococcus a challenging target for vaccine prevention. Meningococcal polysaccharide vaccines against serogroup A and C are efficacious and have been widely used, often in combination with serogroup Y and W135 components. Their relative lack of immunogenicity in young children and infants can be overcome by conjugation to a protein carrier. The effectiveness of serogroup C glycoconjugate vaccines in children of all ages has been demonstrated and they have now been introduced into routine vaccination schedules. Conjugate vaccines against other serogroups, including A, Y, and W135 will soon be available and it is hoped they may emulate this success. Prevention of serogroup B disease has proven more elusive. Several serogroup B vaccines based on outer membrane vesicles have been shown to be immunogenic and reasonably effective in adults and older children, but the protection offered by them is chiefly strain-specific. Multivalent recombinant PorA vaccines have been developed to broaden the protective effect, but no efficacy data are available as yet. Intensive efforts have been directed at other outer membrane protein vaccine candidates and lipopolysaccharide, and some of these have been shown to offer protection in experimental animal models. Nonpathogenic Neisseriae spp. such as Neisseria lactamica are also possible vaccine candidates. Previously unknown proteins have been identified from in silico analysis of the meningococcal genome and their vaccine potential explored. However, none of these has yet been presented as the 'universal' protective antigen and work in this field continues to be held back by our limited knowledge concerning the mechanisms of natural protection against serogroup B meningococci.

Rates of Neisseria meningitidis increasing in young adults

The burden of meningococcal disease has remained unchanged in the United States for the past 4 decades. The currently available meningococcal vaccine is safe and effective, however, due to immunogenic limitations inherent to polysaccharide vaccines, it has been available only for high-risk populations older than 2. Incorporation of a more immunogenic and effective conjugated vaccine into the routine immunization schedule offers an opportunity to substantially affect the incidence of meningococcal disease. The routine use of a meningococcal conjugate vaccine in the United States will save lives and prevent significant morbidity in children and young adults.

Critical analysis of old and new vaccines against N. meningitidis serogroup C, considering the meningococcal disease epidemiology in Brazil

Worldwide, the impact of meningococcal disease is substantial, and the potential for the introduction and spread of more virulent strains of N. meningitidis or strains with increased resistance to current antibiotics causes concern, making prevention essential.

OBJECTIVES

Review the indications for meningococcal disease vaccines, considering the epidemiological status in Brazil.

METHODS

A critical literature review on this issue using the Medline and Lilacs databases.

RESULTS

In Brazil, MenB and MenC were the most important serogroups identified in the 1990s. Polysaccharide vaccines available against those serogroups can offer only limited protection for infants, the group at highest risk for meningococcal disease. Additionally, polysaccharide vaccines may induce a hypo-responsive state to MenC. New meningococcal C conjugate vaccines could partially solve these problems, but it is unlikely that in the next few years a vaccine against MenB that can promote good protection against multiple strains of MenB responsible for endemic and epidemic diseases will become available.

CONCLUSIONS

In order to make the best decision about recommendations on immunization practices, better quality surveillance data are required. In Brazil, MenC was responsible for about 2,000 cases per year during the last 10 years. New conjugate vaccines against MenC are very effective and immunogenic, and they should be recommended, especially for children less than 5 years old. Polysaccharide vaccines should be indicated only in epidemic situations and for high-risk groups. Until new vaccines against MenC and MenB are available for routine immunization programs, the most important measure for controlling meningococcal disease is early diagnosis of these infections in order to treat patients and to offer chemoprophylaxis to contacts.

Reflections on the meningococcal group C infection immunisation campaign: views from the sharp end

In July 1999, the Department of Health launched a campaign to immunise all children aged from 0-17 years with a new vaccine giving protection against meningococcal group C infection. Following the campaign, a survey of Immunisation Co-ordinators in England was conducted to identify strengths and weaknesses of the campaign. This paper summarises the main findings.

Disparity in functional activity between serum anticapsular antibodies induced in adults by immunization with an investigational group A and C Neisseria meningitidis-diphtheria toxoid conjugate vaccine and by a polysaccharide vaccine

Polysaccharide-protein conjugate vaccines elicit higher concentrations of serum anticapsular antibody in infants and children than do unconjugated polysaccharide vaccines. The conjugate-induced antibodies also have higher avidity and complement-mediated bactericidal activity. Similar vaccine-related differences in the magnitude or functional activity of antibody are observed infrequently in immunized adults. We compared the antibody responses of adults immunized with an investigational group A and C meningococcal conjugate vaccine to those elicited by an unconjugated meningococcal polysaccharide vaccine. Although there were no significant differences between the respective geometric mean bactericidal titers of the two vaccine groups, it took, on average, three- to fourfold higher concentrations of polysaccharide-induced serum anticapsular antibody to achieve 50% complement-mediated bacteriolysis than conjugate-induced antibody (P < 0.001 for groups A and C). At limiting doses, the polysaccharide-induced anticapsular antibodies also were less effective in conferring passive protection against meningococcal bacteremia in infant rats challenged with a group C strain (P < 0.04). The avidity index of the group C antibodies was higher in the conjugate vaccine group than in the polysaccharide vaccine group (P < 0.005). The disparities in the functional activity of the anticapsular antibodies elicited in adults by the two vaccines imply fundamental differences in the respective B-cell populations stimulated.

Safety and efficacy of meningococcal group C conjugate vaccines

The UK was the first country to implement a universal vaccination programme with conjugate polysaccharide vaccines against Neisseria meningitidis group C. This article reviews the pre- and postlicensure data on their efficacy and safety 3 years after the introduction of the programme. Local reactogenicity data compare favourably with other routine vaccinations and no specific increase in adverse reactions has been associated with their use in infant vaccination programmes. Self-limiting systemic reactions such as fever, myalgia, headaches and irritability have commonly been observed in prelicensure studies. Passive postlicensure safety monitoring of suspected adverse reactions has identified a large number of reports, generally of reactions deemed non-serious and reversible. An Expert Working Group has concluded the balance of benefits and risks to be overwhelmingly favourable. Further safety data are expected from large data-linkage studies. Present efficacy estimates, based on active surveillance of case numbers, vaccine failures and coverage rates, are approximately 90% for all age groups. A significant fall in the number of cases attributable to meningococcal group C infection has been observed in the age group of < 20 years. The annual number of fatalities from confirmed meningococcal C disease in the same population has fallen from 67 to 5 cases within a 2-year period.

A glycoconjugate vaccine for Neisseria meningitidis induces antibodies in human infants that afford protection against meningococcal bacteremia in a neonate rat challenge model

The functional activities of serum samples from human infants immunized with a glycoconjugate vaccine for Neisseria meningitidis serogroup C were assessed in a complement-mediated antibody-dependent serum bactericidal assay (SBA) and in a neonate rat model of protection from bacteremia. Selective serum samples from individual human infants were combined to make a panel of 11 serum pools to obtain a sufficient volume for testing. Each pool was assayed (i) for the anti-N. meningitidis serogroup C capsular polysaccharide (PS) immunoglobulin G (IgG) concentration as determined by reactivity in a direct-binding enzyme-linked immunosorbent assay, (ii) for bactericidal activity against N. meningitidis serogroup C strain C11, and (iii) for the ability to reduce bacteremia after passive transfer into a neonate rat model. Representative serum samples from infants who were not previously immunized with any N. meningitidis serogroup C vaccine served as a negative control. The prepared serum pools ranged in antibody concentration from 0.18 to 17.31 micro g of IgG specific for N. meningitidis serogroup C PS per ml. For this serum panel, a direct relationship between concentrations of anti-N. meningitidis serogroup C PS-specific IgG and serum SBA titers (r = 0.9960) was observed. Passive transfer to neonate rats demonstrated the ability of postimmunization serum samples to significantly reduce (> or =2-log(10) reduction compared to control animals) the level of bacteremia following a challenge. Of 79 neonate rats that received > or =0.031 micro g of human infant anti-N. meningitidis serogroup C PS IgG, 75 (94.9%) had a > or =2-log(10) reduction in bacteremia, whereas of the animals that received <0.031 micro g of antigen-specific IgG, 10.3% (4 of 39 rats) showed a > or =2-log(10) reduction in bacteremia. It was concluded that the anti-N. meningitidis serogroup C PS IgG antibody induced by this glycoconjugate vaccine had in vitro functional activity (as determined by a SBA) and also afforded protection against meningococcal bacteremia in an animal model.

Prior meningococcal A/C polysaccharide vaccine does not reduce immune responses to conjugate vaccine in young adults

The immune responses induced in young adults by a meningococcal A/C polysaccharide-diphtheria toxoid conjugate vaccine (Mcj) and a meningococcal A/C plain polysaccharide vaccine (Mps) were evaluated in unvaccinated subjects and those who had received either vaccine previously. 195 subjects aged 17-30 years received either Mps or Mcj. After 12 months, they were randomised again to receive a second dose of either vaccine. Serogroup specific serum bactericidal assay (SBA) titers and IgG antibody responses were assayed before and 4-8 weeks after primary and booster immunisation. Both vaccines were immunogenic in previously unvaccinated subjects. Administration of a dose of Mps after previous Mps or Mcj induced lower bactericidal titers to group C Neisseria meningitidis than those seen after a single dose of Mps. Bactericidal antibody responses to Mcj were not reduced in subjects who had previously received Mps.

Meningococcal disease: how to prevent and how to manage

Meningococcal disease is a significant problem in the paediatric population. The diagnosis of meningococcal disease can be problematic and progression of the disease can rapidly lead to a life-threatening illness. Despite the success of antibiotic treatment, mortality rates remain high. The development of protein-polysaccharide conjugate vaccines has significantly improved the success of vaccination in reducing the incidence of meningococcal disease. However, a comprehensive vaccine conferring protection against disease-associated serogroups remains elusive. The aim of this review is to highlight recent significant improvements in the prevention and management of meningococcal disease.

Meningococcal serogroup C conjugate vaccine

Meningococcal meningitis and septicaemia are important causes of morbidity and mortality in many parts of the world. More than 90% of the cases are caused by serogroups A, B and C; the remaining 10% are largely caused by the W-135 and Y strains. During the mid-to-late 1990s there was an increase in meningococcal serogroup (MS) C disease in the UK and some parts of Europe. MS C polysaccharide vaccines that were developed in the 1960s are weakly immunogenic and not protective in infants under 2 years of age, but are effective in older recipients. Meningitec (Wyeth-Ayerst) is produced by conjugation of serogroup C oligosaccharide with a mutant diphtheria protein (CRM197), with the aim of inducing T-cell dependent immune responses. It has been found to be immunogenic in infants, toddlers, older children and adults. The vaccine has also been shown to induce immunological memory and therefore is likely to give long-term protection against disease. It received a license for use in the UK in October 1999 and was introduced into the UK immunisation schedule in November 1999. Surveillance studies after introduction of this and similar vaccines have demonstrated a dramatic fall in the incidence of MS C disease. Pre-licensure research studies and post-licensure adverse event data have confirmed that the vaccine is safe.

Safety of a new conjugate meningococcal C vaccine in infants

BACKGROUND

Group C conjugate meningococcal vaccines (Men C) were introduced into the UK primary immunisation schedule in November 1999. There has been extensive professional and public interest in their efficacy and safety.

AIM

To determine the occurrence of at least one uncommon adverse event in infants related to the administration of the Chiron Men C vaccine.

METHODS

A total of 2796 infants aged approximately 2 months were recruited into the study from areas in and around Sheffield and from Scotland. They were vaccinated with the Chiron Men C vaccine at 2, 3, and 4 months along with routine immunisations. Data on adverse events occurring one month after each dose were collected actively and prospectively and reviewed for possible relation to the vaccine.

RESULTS

There were no deaths. There were no serious adverse events considered definitely or probably caused by the vaccine. Four infants developed serious adverse events (hypotonia, screaming syndrome, maculopapular rash, and agitation, respectively) that were considered possibly related to the vaccine. All recovered completely. Adverse events were seen in 1804 children but were considered possibly related to the vaccine in only 49 (1.8%). On subsequent immunisation there were no recurrences of adverse events considered to be possibly related to the vaccine.

Planning, registration, and implementation of an immunisation campaign against meningococcal serogroup C disease in the UK: a success story

The introduction of meningococcal C conjugate (MCC) vaccine in the UK in November 1999 as a routine 3 dose infant immunisation course, with a single catch-up dose for all children aged between 12 months and 17 years, was the result of an intensive 5 year collaborative research programme funded by the Department of Health for England and involving public bodies, academia and vaccine manufacturers. The research programme established the safety and immunogenicity of MCC vaccines in infants, toddlers, pre-school and school-aged children. The nature and frequency of common adverse events in school-aged children was similar to that after a booster dose of diphtheria and tetanus vaccine given to the same age groups. The recommendation that a single dose was adequate for children aged 12 months and above was based on antibody levels measured by serum bactericidal assay and evidence of induction of immunological memory as shown by maturation of antibody avidity. Licensure by the Medicines Control Agency was based on serological criteria alone without direct evidence of efficacy and has set a precedent for other meningococcal conjugate polysaccharide vaccines. Vaccine coverage of around 85% was achieved in the targeted age groups and has resulted in a drop in the incidence of serogroup C disease in these groups of over 80% within 18 months of the start of the vaccination programme. Early post-licensure efficacy estimates for toddlers and teenagers (88 and 96%, respectively, in the first 16 months after vaccination) validate the serological criteria used for licensure. Surveillance of the prevalent serogroups and serosubtypes among invasive case isolates has shown no evidence of any capsular switching to serogroup B during the first 18 months of the MCC vaccination programme.