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Update on prevention of meningococcal disease: focus on tetravalent meningococcal conjugate vaccine.

OBJECTIVE: To review the immunogenicity, efficacy, safety, and new recommendations for routine use of the tetravalent meningococcal conjugate vaccine (MCV4). DATA SOURCES: A MEDLINE search (1966-June 2005) was conducted using the key words Neisseria meningitidis and meningococcal vaccines for clinical trials limited to human research published in the English language. STUDY SELECTION AND DATA EXTRACTION: Randomized, controlled, multicenter trials were reviewed and included to evaluate the safety and efficacy of MCV4. Additional open-label trials on the use of MCV4 in children less than 24 months of age are included since these studies may be used to support the approval of the vaccine for use in children. Literature on epidemiology and pathology of meningococcal meningitis and the Advisory Committee on Immunization Practices (ACIP) recommendations were also reviewed. DATA SYNTHESIS: MCV4 is approved for active immunization of adolescents and adults between the ages of 11 and 55 years for the prevention of disease caused by N. meningitidis serogroups A, C, Y, and W-135. MCV4 has been shown to have comparable immunogenicity and a similar adverse reaction profile to the tetravalent meningococcal polysaccharide vaccine (MPSV4). It is expected that MCV4 will provide a longer duration of protection from meningococcal disease than MPSV4. CONCLUSIONS: Based on lished immunogenicity, efficacy, and safety data, as well as the recent recommendations by the ACIP for its routine use, MCV4 is the preferred meningococcal vaccine for persons between 11 and 55 years of age and should be included on pharmacy formularies.

Clinical Trials as Topic↗

Molecular techniques for the investigation of meningococcal disease epidemiology.

Meningococcal disease remains a major cause of childhood morbidity and mortality world wide and no comprehensive vaccine is available against the causative organism, Neisseria meningitidis. Molecular studies of the diversity of this bacterium have provided a number of key insights into its biology, which have implications for control of meningococcal disease. These have included the identification of hyperinvasive lineages and the correlation of genetic type with antigenic type and disease epidemiology. In practical terms, such studies have enabled the application of DNA-based technologies in the development of improved methods for diagnosis and epidemiological monitoring. These data are of especial importance with the current, and ongoing, development and introduction of new meningococcal vaccines.

Antigens, Bacterial↗

Prospects offered by genome studies for combating meningococcal disease by vaccination.

Meningococcal disease was first recognised and Neisseria meningitidis isolated as the causative agent over 100 years ago, but despite more than a century of research, attempts to eliminate this distressing illness have so far been thwarted. The main problem lies in the fact that N. meningitidis usually exists as a harmless commensal inhabitant of the human nasopharynx, the pathogenic state being the exception rather than the norm. As man is its only host, the meningococcus is uniquely adapted to this ecological niche and has evolved an array of mechanisms for evading clearance by the human immune response. Progress has been made in combating the disease by developing vaccines that target specific pathogenic serogroups of meningococci. However, a fully comprehensive vaccine that protects against all pathogenic strains is still just beyond reach. The publication of the genome sequences of two meningococcal strains, one each from serogroups A and B and the imminent completion of a third illustrates the extent of the problems to be overcome, namely the vast array of genetic mechanisms for the generation of meningococcal diversity. Fortunately, genome studies also provide new hope for solutions to these problems in the potential for a greater understanding of meningococcal pathogenesis and possibilities for the identification of new vaccine candidates. This review describes some of the approaches that are currently being used to exploit the information from meningococcal genome sequences and seeks to identify future prospects for combating meningococcal disease.

Clinical Trials as Topic↗

Vaccines against meningococcal disease: current and future technologies.

Development of the meningococcal serogroup C conjugate vaccine and its national implementation in the UK has been a major breakthrough in the prevention of meningococcal disease. New technologies are increasing the likelihood that research towards a vaccine against group B meningococcus will be successful. This review covers the recent development of vaccines against meningococcal disease and examines future vaccine candidates. The development of meningococcal polysaccharide vaccines was based on the virulence of the bacterial capsule components. The immunogenicity of these vaccines has been improved by covalent linkage to proteins in the new meningococcal C conjugate vaccines. However, the most promising developments for serogroup B disease have stemmed from other virulence determinants such as outer membrane proteins (OMPs) and lipopolysaccharides (LPS). New genome sequencing technology promises a way forward to developing a broadly cross-protective vaccine for this important pathogen.

Adolescent↗

Meningococcal conjugate vaccines.

Disease caused by Neisseria meningitidis is associated with high mortality rates and significant sequelae. Polysaccharide meningococcal vaccines have been available for > 20 years, and have been used in travellers to control outbreaks, and in some countries for adolescents entering college, although they provide only a short duration of immunity and do not produce a herd effect. Monovalent and quadrivalent (A, C, Y, W-135) meningococcal conjugate vaccines have recently been licensed and endorsed for use in infants, children, adolescents and adults in various countries. Among the key features of the new meningococcal conjugate vaccines are stimulation of both B cell-dependent and T cell-dependent immune responses, induction of immunological memory and booster effects, longer-term protection, reduction of nasopharyngeal carriage of N. meningitidis, and herd immunity. Large, randomised, double-blind studies in adults, adolescents, children and infants have demonstrated the immunogenicity and safety of the new meningococcal conjugate vaccine formulations.

Animals↗

Meningococcal disease prevention and control strategies for practice-based physicians (Addendum: recommendations for college students). Committee on Infectious Diseases.

The numbers of reported cases of meningococcal disease in 15- to 24-year-olds and outbreaks of meningococcal serogroup C disease, including outbreaks in schools and other institutions, have increased during the past decade. In response to outbreaks on college campuses, the American College Health Association has taken an increasingly proactive role in alerting college students and their parents to the risk of this disease and informing them about the availability of an effective vaccine. Recent epidemiologic studies have demonstrated an increased risk of disease in college students living in dormitories, particularly among freshmen, compared with similarly aged persons in the general population. At least 60% of these cases are potentially preventable by vaccination with the quadrivalent meningococcal A, C, Y, and W-135 polysaccharide vaccine. These findings support immunization of college students, particularly freshmen living in dormitories. Hence, college students and their parents should be informed by health care professionals at routine prematriculation visits and during college matriculation of the risk of meningococcal disease and potential benefits of immunization. Vaccine should be made available to those requesting immunization. College and university health services also should facilitate implementation of educational programs concerning meningococcal disease and availability of immunization services.

Academies and Institutes↗

Cost-effectiveness of conjugate meningococcal vaccination strategies in the United States.

CONTEXT: The US Food and Drug Administration approved a meningococcal conjugate A/C/Y/W-135 vaccine (MCV-4) for use in persons aged 11 to 55 years in January, 2005; licensure for use in younger age groups is expected in 2 to 4 years. OBJECTIVE: To evaluate and compare the projected health and economic impact of MCV-4 vaccination of US adolescents, toddlers, and infants. DESIGN: Cost-effectiveness analysis from a societal perspective based on data from Active Bacterial Core Surveillance (ABCs) and other published and unpublished sources. Sensitivity analyses in which key input measures were varied over plausible ranges were performed. SETTING AND PATIENTS: A hypothetical 2003 US population cohort of children 11 years of age and a 2003 US birth cohort. INTERVENTIONS: Hypothetical routine vaccination of adolescents (1 dose at 11 years of age), toddlers (1 dose at 1 year of age), and infants (3 doses at 2, 4, and 6 months of age). Each vaccination scenario was compared with a "no-vaccination" scenario. MAIN OUTCOME MEASURES: Meningococcal cases and deaths prevented, cost per case prevented, cost per life-year saved, and cost per quality-adjusted life-year saved. RESULTS: Routine MCV-4 vaccination of US adolescents (11 years of age) would prevent 270 meningococcal cases and 36 deaths in the vaccinated cohort over 22 years, a decrease of 46% in the expected burden of disease. Before program costs are counted, adolescent vaccination would reduce direct disease costs by $18 million and decrease productivity losses by $50 million. At a cost per vaccination (average public-private price per dose plus administration fees) of $82.50, adolescent vaccination would cost society $633000 per meningococcal case prevented and $121000 per life-year saved. Key variables influencing results were disease incidence, case-fatality ratio, and cost per vaccination. The cost-effectiveness of toddler vaccination is essentially equivalent to adolescent vaccination, whereas infant vaccination would be much less cost-effective. CONCLUSIONS: Routine MCV-4 vaccination of US children would reduce the burden of disease in vaccinated cohorts but at a relatively high net societal cost. The projected cost-effectiveness of adolescent vaccination approaches that of recently adopted childhood vaccines under conditions of above-average meningococcal disease incidence or at a lower cost per vaccination.

Adolescent↗

Prevention and control of meningococcal disease: recommendations for use of meningococcal vaccines in pediatric patients.

Two peaks in the incidence of invasive meningococcal disease (IMD) occur in pediatric patients: infants younger than 1 year and adolescents 15 to 18 years of age. Although the incidence of IMD is highest in infants, the case-fatality rate is highest in adolescents (approximately 20%). Epidemiologic studies also have demonstrated increased risk of IMD among college freshman living in dormitories compared with other college students and similarly aged persons in the general population. At least 75% of cases of IMD in 11- to 18-year-olds are caused by serogroups A, C, Y, and W-135; thus, IMD potentially is preventable by immunization with quadrivalent meningococcal vaccines. Meningococcal A, C, Y, W-135 conjugate vaccine (MCV4) was licensed in 2005 for use in people 11 to 55 years of age. On the basis of data indicating increased risk of meningococcal disease and fatality among certain adolescents and college students, the American Academy of Pediatrics recommends administration of MCV4 to young adolescents (at the 11- to 12-year visit), students entering high school or 15-year-olds, and college freshmen who will be living in dormitories. For pediatric patients 11 years and older who are at increased risk of meningococcal disease, MCV4 also is recommended. The purposes of this statement are to provide the rationale for routine use of MCV4 in adolescents and to update recommendations for use of the meningococcal polysaccharide vaccine in pediatric patients.

Adolescent↗

Serologic correlates of protection for evaluating the response to meningococcal vaccines.

Meningococci cause serious disease worldwide and the organism remains the most common cause of bacterial meningitis in children and young adults. The only effective means of controlling disease is through vaccination. Although polysaccharide vaccines have been available for serogroup A, C, Y and W135 for many years, serogroup C polysaccharide-protein conjugate vaccines have only recently been licensed in many countries. Conjugate vaccines for combinations of serogroup A, C, Y and W135 are progressing through clinical trials and major efforts are being made to develop a safe and efficacious vaccine against serogroup B. To assess the quality of the immune response after vaccination, laboratory correlates of protection are needed. For serogroups A and C, serum bactericidal antibody is a well established predictor for protection but for serogroup B, other mechanisms besides serum bactericidal antibody may also be involved in conferring protection against disease. The serologic correlates of protection for evaluating the response to meningococcal vaccines are described in this review.

Age Factors↗

Can Neisseria lactamica antigens provide an effective vaccine to prevent meningococcal disease?

Neisseria lactamica is a commensal organism that is closely related to Neisseria meningitidis, the causative agent of meningococcal disease. N. lactamica has many antigens in common with N. meningitidis, but it lacks a polysaccharide capsule and the serosubtyping antigen PorA. Carriage studies have demonstrated that N. lactamica is carried in the nasopharynx of young children at a time when meningococcal carriage is rare. However, natural immunity to meningococcal disease develops during this period and carriage of commensal Neisseria is implicated in the development of this immunity. Recent studies have characterized the antigens which may be responsible for inducing a crossreactive antibody response and have demonstrated that N. lactamica-based vaccines can protect in experimental models of meningococcal disease. The potential for these vaccines to be effective in preventing meningococcal disease is discussed.

Antigens, Bacterial↗

Host response to Neisseria meningitidis lacking lipopolysaccharides.

Plasma levels of lipopolysaccharides are closely associated with disease manifestations and outcomes in meningococcal infections. The knockout mutant lpxA-Neisseria meningitidis completely lacking lipopolysaccharides has made it possible to study the contribution of nonlipopolysaccharide molecules in the bacterial cell wall to the host's response. The lpxA-N. meningitidis requires 10- to 100-fold higher concentrations of bacteria to elicit the same level of pro-inflammatory cytokines (tumor necrosis factor-alpha, interleukin-1beta and -6) as the wild type parent strain. It activates human mononuclear peripheral blood cells through CD14 and Toll-like receptor-2 receptor complex whereas the wild type strain activates these cells through the CD14-Toll-like receptor-4-MD2 pathway. Dendritic cells are hardly activated by the lpxA-N. meningitidis. It is as efficient as the wild type strain in activating complement. The lpxA-N. meningitidis expresses pili but does not adhere or invade mucosal cells normally. The defensin-mediated adhesion of lpxA-N. meningitidis to the respiratory epithelial cells is severely reduced as compared with the wild-type strain.

Bacterial Adhesion↗

The epidemiological impact of antimeningococcal B vaccination in Cuba.

The incidence of invasive meningococcal disease (IMD) before (1984-1988) and after (1989-1994), a nationwide intervention with VA-MENGOC-BC vaccination started in 1989, was compared. The prevaccination period incidence density (ID> 8.8/10(5) year-person) was higher than the postvaccination ID (ID< 6.5/10(5) year-person). The percentage proportional differences from the start to the end of each period of ID in the vaccinal period was higher (87%) than the prevaccinal (37%) with significant differences among vaccinated groups (< 25 years old). A break-point (Chow test) was confirmed by the decrease in the ID between 1989 and 1990 in children under 1 year old, 5-9, 10-14, 15-19 and 50-54 years. Comparison of ID using maps showed a decrease in IMD in all municipalities during the postvaccination period. These findings support the epidemiological impact of VA-MENGOC-BC vaccination in the reduction of IMD morbidity.

Adolescent↗

[Impact of systematic vaccination with the antimeningococcal C conjugated vaccine in a health area in Andalusia].

BACKGROUND: A retrospective longitudinal study of population incidence was made to assess the effectiveness of meningococcal serogroup C conjugate vaccine, after its mass introduction in children in the geographic area of a health district, measuring its population impact, and we have studied the state of the meningococcal disease. METHODS: Vaccine coverage in children born between 1991 and 2001, and rates of incidence in declared cases of meningococcal disease in seven epidemiological seasons (1997/98 to 2003/04) were calculated. The impact of vaccination against serogroup C meningitis was assessed comparing the average annual rates of previous and later seasons to the vaccination campaigns in population younger and older than 10, using the Fisher exact test. RESULTS: In all the study period, 109 cases of meningococcal disease were declared, of which 50 were of serogroup C meningococcal disease. Starting from 2000/2001 season the incidence of serogroup C disease decreased in the population below 10. In this age group, the annual average rate of post-vaccine seasons decreases in respect to pre-vaccine (from 8.2 to 2.0 per 100,000 inhabitants) showing a statistically significant difference. In the population above 10 years, this incidence reduction was not observed. In the study period, no case of vaccine failure was declared. CONCLUSIONS: The absence of vaccine failure and the impact observed on the incidence of serogroup C meningococcal disease in children under 10 suggests the effectiveness of this new conjugate vaccine, together with suitable vaccination conditions (vaccination schedule, high catch-up, etc.) which are developing in our health district.

Age Factors↗

Effectiveness of a mass immunization campaign against serogroup C meningococci in children in the federal state of Santa Catarina, Brazil.

In addition to vaccine efficacy studies, there is a pressing need to evaluate vaccine effectiveness in a way that takes into account the limitations of health care systems in certain settings. An attempt to reach this objective was exemplified by a vaccination campaign against serogroup C meningococci in the federal state of Santa Catarina, in Brazil. A polysaccharide vaccine against serogroup C meningococci was administered to all individuals between 6 months and 14 years of age in March, 1996, in the municipalities that had the highest incidence of meningococcal disease in the previous year. All cases of the disease due to this serogroup observed in Santa Catarina during a 1-year period before and after the vaccination were included in the analysis. The cumulative incidence rate ratio was calculated for the unvaccinated compared to the vaccinated area. As a second step, the ratio of this quantity for the period before and after the vaccination, i.e. the ratio of the rate ratios (RRR), was calculated. One minus RRR was used to estimate the vaccine effectiveness. In the general population, the vaccine effectiveness was 74.3% (95% confidence intervals 52.7% to 99.6%). In children 6 months to 14 years, vaccine effectiveness was 93.1% (85.2% to 100%). Vaccine effectiveness could not be confirmed within more specific age bands, probably due to the lack of statistical power. It is concluded that group C meningococcal vaccine is effective in reducing the occurrence of meningococcal disease in children 6 months to 14 years of age, and that the ratio of rate ratios (RRR) in a useful method to evaluate vaccine effectiveness.

Adolescent↗

The effect of antibiotics on mortality from infectious diseases in Sweden and Finland.

A study was carried out to determine whether the preexisting decline in mortality rates from infectious diseases accelerated after the introduction of antibiotic and chemotherapeutic drugs. Linear regression curves showed that in Sweden mortality rates declined faster in septicemia, syphilis, and non-memingococcal meningitis after the introduction of these drugs. By contrast, for the ten other infectious diseases studied, (scarlet fever, erysipelas, acute rheumatic fever, puerperal sepsis, meningococcal infection, bronchitis, pneumonia, tuberculosis, typhoid fever, and acute gastroenteritis) no such accelerated decline in mortality could be detected. The findings suggest that antibiotic and chemotherapeutic drugs have not had the dramatic effect of the mortality of infectious diseases popularly attributed to them.

Age Factors↗

Should college students be vaccinated against meningococcal disease? A cost-benefit analysis.

Outbreaks and sporadic cases of meningococcal disease among college students have prompted consideration of a policy of routine vaccination for this group. Purchase and administration of the vaccine for routine vaccination would cost $56 million per year. Savings in medical care and indirect costs would not equal this amount unless the annual rate of disease among students is at least 6.5/100,000. The actual rate among students is unknown; however, surveillance data suggest it could not be more than 1.3/100,000. At rates near this estimate, the net cost of the program would be approximately $45 million annually. More cost-effective prevention strategies might be yielded by further studies to identify students at substantial risk of meningococcal disease, or by the development of a conjugate serogroup C vaccine that could be administered during infancy.

Adolescent↗

Meningococcal vaccines. Current status and future possibilities.

Meningococcal disease causes great emotion and anxiety in the families and caregivers of patients. Numbers of such patients are usually small in industrialised countries, unlike those in many regions--especially in subsahelian Africa. Vaccines have been tried for more than 80 years; at present there are available polysaccharide vaccines against groups A, C, Y and W135, and a protein-based vaccine against group B. A property common to all is their relative efficacy (75 to 100%) at school age and after, and an acceptably short persistence of antibodies. Small children pose the major challenge, in whom there is essentially evidence of clinical protection only against group A and C diseases. With vaccines against other serogroups protection is possible, but not yet proven in controlled clinical studies. The search is on for help from various modifications, including the conjugation technique, to transform the independent nature of polysaccharide response towards T cell dependence, as was done earlier in Haemophilus influenzae type b vaccines. First trials along this path are encouraging although, again, group B meningococci pose special problems. The next few years will probably see a new generation of meningococcal vaccines. Generally speaking, the incidence of meningococcal disease is too low to indicate vaccinations for the whole population, or even children, but some risk groups and epidemics are important exceptions. To date, bivalent group A + C or tetravalent group A + C + Y + W135 polysaccharides, or an outer membrane protein-based group B vaccine, are the products to be used when the indications, that may vary from country to country, are considered met. A strong herd immunity effect, demonstrated with group A and C vaccinations, facilitates extinction of an epidemic since large-scale vaccinations can be restricted only in the major risk groups, children and in various schools. Prompt intervention demands, however, a functioning mechanism which detects very early on a pending epidemic. Unfortunately, such a mechanism is often lacking in countries often hit by this deadly disease.

Adolescent↗