Shift in the age-distribution of meningococcal disease as predictor of an epidemic?

Temporal variations in the serogroup distribution of invasive meningococcal disease in Quebec, Canada, due to emerging unique clade of serogroup Y strain belonging to the Sequence Type-23 clonal complex

OBJECTIVE

To identify recent trends in invasive meningococcal diseases (IMD) in Quebec, Canada, with a focus on MenY cases and MenY strains.

METHODS

IMD cases and MenY strains from January 1, 2015 to August 11, 2023 were analyzed for clonal analysis and prediction of susceptibility to MenB vaccines. MenY strains of ST-23 CC from Quebec were analyzed with global MenY strains by core-genomic multi-locus sequence typing (cg-MLST).

RESULTS

Since 2015 the serogroup distribution of IMD in Quebec has shifted from predominantly MenB to mainly MenY, with most (80.9 %) of the latter belonging to ST-23 CC. The median age of MenY cases due to ST-23 CC were statistically younger than MenY cases due to non-ST-23 CC. MenY of ST-23 CC showed genetic diversity and the major genetic cluster were similar to the Swedish Y1 strain. The increase in invasive MenY disease in Quebec was due to a sub-clade of Lineage 23.1 which caused an elevated proportion of severe disease in young adults.

CONCLUSION

The increase in invasive MenY disease in Quebec, Canada was driven by the expansion of a sub-clade of Lineage 23.1 in young adults. Currently available quadrivalent A,C,W,Y-conjugate meningococcal vaccines were predicted to provide protection against these strains.

Clinical manifestations of invasive meningococcal disease in Victoria with the emergence of serogroup W and serogroup Y Neisseria meningitidis

BACKGROUND

Historically, Australian cases of invasive meningococcal disease (IMD) have been most frequently caused by Neisseria meningitidis serogroup B, but recently an increase in cases due to serogroup W (MenW) and serogroup Y (MenY) has occurred.

AIM

To determine whether clinical manifestations of IMD have changed due to increased incidence of MenW and MenY.

METHODS

We performed a retrospective review of IMD cases notified to the Department of Health and Human Services in Victoria, Australia. We compared the period between January 2013 and June 2015 (defined as P1) immediately before the increase in MenW and MenY was noted, with the equal time period of July 2015 to December 2017 (P2), when this increase was observed.

RESULTS

IMD was notified more frequently in P2 than P1 (1.24 vs 0.53 per 100 000 person-years, P < 0.001). IMD cases in P2 were older (46 vs 19 years, P < 0.001), and more likely due to MenW (92/187, 49.2% vs 11/80, 13.8%, P < 0.001) or MenY (31/187, 16.6% vs 4/80, 5.0%, P = 0.01). IMD cases from P2 were more likely bacteraemic (151/187, 80.7% vs 55/80, 68.8%, P = 0.04), while meningitis (68/187, 36.4% vs 41/80, 51.3%, P = 0.03) and rash (65/181, 35.9% vs 45/78, 57.7%, P = 0.002) were less frequent. Intensive care unit admission rates and in-hospital mortality were unchanged.

CONCLUSION

Alongside an increase in IMD in Victoria, the proliferation of cases of MenW and MenY occurred in older patients, and were more often identified through bacteraemia rather than meningitis or purpura fulminans. Clinicians should be aware of these changes to facilitate earlier identification and treatment of IMD.

Dissemination of the ST-103 clonal complex serogroup C meningococci in Salvador, Brazil

Invasive meningococcal disease (IMD) is a major public health problem worldwide. An epidemic of serogroup C (NmC) IMD occurred in 2010 in the city of Salvador. In this study, we describe the antigenic and genetic characterization of meningococcal isolates collected from meningitis cases in Salvador from 2001 to 2012. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were performed for the analysis of IMD isolates. A total of 733 cases were identified, and the serogroup was determined for 391 (53.0%) of these. Most cases were caused by NmC (53%) or B (47%). The most prevalent strains were B:4,7:P1.19,15 (32.9%; 129/391) and C:23:P1.14-6 (28.6%; 112/391). Based on PFGE/MLST analysis, 71.3% (77/108 PFGE-tested isolates) clustered as two clones of sequence type ST-3779 and ST-3780, both belonging to the ST-103 clonal complex. ST-3779 has been detected in Salvador since 1996 and together with ST-3780 became predominant after 2005. There was a predominance of C:23:P1.14-6, ST-3779/3780 in Salvador during the period of 2007-2012, establishing a major clonal lineage, which remained in the community for a long time; this has serious implications for public health, particularly in terms of prevention and control strategies of IMD.

Meningococcal disease in the Asia-Pacific region: Findings and recommendations from the Global Meningococcal Initiative

The Global Meningococcal Initiative (GMI) is a global expert group that includes scientists, clinicians, and public health officials with a wide range of specialties. The purpose of the Initiative is to promote the global prevention of meningococcal disease (MD) through education, research, and cooperation. The first Asia-Pacific regional meeting was held in November 2014. The GMI reviewed the epidemiology of MD, surveillance, and prevention strategies, and outbreak control practices from participating countries in the Asia-Pacific region.Although, in general, MD is underreported in this region, serogroup A disease is most prominent in low-income countries such as India and the Philippines, while Taiwan, Japan, and Korea reported disease from serogroups C, W, and Y. China has a mixed epidemiology of serogroups A, B, C, and W. Perspectives from countries outside of the region were also provided to provide insight into lessons learnt. Based on the available data and meeting discussions, a number of challenges and data gaps were identified and, as a consequence, several recommendations were formulated: strengthen surveillance; improve diagnosis, typing and case reporting; standardize case definitions; develop guidelines for outbreak management; and promote awareness of MD among healthcare professionals, public health officials, and the general public.

Effectiveness of meningococcal C conjugate vaccine in Salvador, Brazil: a case-control study

Background

During a citywide epidemic of serogroup C meningococcal disease in Salvador in 2010, Brazil, the state government initiated mass vaccination targeting two age groups with high attack rates: individuals aged <5 years and 10–24 years. More than 600,000 doses of meningococcal serogroup C conjugate vaccines were administered. We performed a case-control study to evaluate vaccine uptake, document vaccine effectiveness and identify reasons for non-vaccination.

Methods and Findings

Population-based surveillance identified patients with laboratory-confirmed invasive meningococcal C (MenC) disease during 2010. Information on MenC vaccination was obtained from case patients and age-matched individuals from the same neighborhoods. MenC vaccine effectiveness was estimated based on the exact odds ratios obtained by conditional logistic regression analysis. Of 51 laboratory-confirmed cases of serogroup C meningococcal disease among patients <5 and 10–24 years of age 50 were included in the study and matched with 240 controls. Overall case-fatality was 25%. MenC vaccine coverage among controls increased from 7.1% to 70.2% after initiation of the vaccination campaign. None of the 50 case patients but 70 (29.2%) of the 240 control individuals, including 59 (70.2%) of 84 matched with cases from the period after MenC vaccination, had received at least one MenC vaccine dose. Overall effectiveness of MenC was 98% with a lower 95% exact confidence limit of 89%.

Conclusions

MenC vaccines administered during the meningococcal epidemic were highly effective, suggesting that rapid vaccine uptake through campaigns contributed to control of meningococcal disease.

Global epidemiology of invasive meningococcal disease

Neisseria meningitidis is one of the leading causes of bacterial meningitis globally and can also cause sepsis, pneumonia, and other manifestations. In countries with high endemic rates, the disease burden places an immense strain on the public health system. The worldwide epidemiology of invasive meningococcal disease (IMD) varies markedly by region and over time. This review summarizes the burden of IMD in different countries and identifies the highest-incidence countries where routine preventive programs against Neisseria meningitidis would be most beneficial in providing protection. Available epidemiological data from the past 20 years in World Health Organization and European Centre for Disease Prevention and Control collections and published articles are included in this review, as well as direct communications with leading experts in the field. Countries were grouped into high-, moderate-, and low-incidence countries. The majority of countries in the high-incidence group are found in the African meningitis belt; many moderate-incidence countries are found in the European and African regions, and Australia, while low-incidence countries include many from Europe and the Americas. Priority countries for vaccine intervention are high- and moderate-incidence countries where vaccine-preventable serogroups predominate. Epidemiological data on burden of IMD are needed in countries where this is not known, particularly in South- East Asia and Eastern Mediterranean regions, so evidence-based decisions about the use of meningococcal vaccines can be made.

Laboratory-based surveillance of Neisseria meningitidis isolates from disease cases in Latin American and Caribbean countries, SIREVA II 2006-2010

BACKGROUND

Published data on the epidemiology of meningococcal disease in Latin America and the Caribbean region is scarce and, when available, it is often published in Spanish and/or in non-peer-reviewed journals, making it difficult for the international scientific community to have access.

METHODS

Laboratory data on 4,735 Neisseria meningitidis strains was collected and reported by the National Reference Laboratories in 19 Latin American countries and the Caribbean Epidemiology Centre (CAREC) between 2006 and 2010 as part of the work carried out by the SIREVA II network. Serogroup and MIC to penicillin, rifampin and chloramphenicol were determined.

RESULTS

Isolates were mainly obtained from patients <5 years, but each year around 25% of isolates came from adult patients. Serogroup distribution was highly variable among countries. Serogroup C was the main cause of disease in Brazil; the majority of disease seen in the Southern cone was caused by serogroup B, but serogroup W135 strains have increased in recent years. In the Andean and Mexico, Central America and Caribbean regions, serogroups B and C were equally present, and serogroup Y was frequently isolated. Isolates were generally susceptible to chloramphenicol, penicillin and rifampin, but almost 60% of isolates characterized in Southern cone countries presented intermediate resistance to penicillin. Five rifampin-resistant isolates have been isolated in Uruguay and Brazil.

CONCLUSIONS

Serogroup distribution is highly variable among countries, but some geographic structuring can be inferred from these data. Epidemiological and laboratory data are scarce among Andean and Mexico, Central America and Caribbean countries. Evaluation and implementation of corrective measures on disease surveillance and reporting systems and the implementation of molecular diagnostic techniques and molecular characterization on meningococcal isolates are advised.

The epidemiology of meningococcal disease in Latin America 1945-2010: an unpredictable and changing landscape

Meningococcal disease is mostly endemic in Latin America, with periodic occurrences of outbreaks and epidemics over the last few decades. This literature review summarizes the available epidemiological data for this region between 1945 and 2010. Incidence rates and serogroup distribution differ from country to country and over time. Serogroups A, B, and C have all been major causes of meningococcal disease since the 1970s. In the last decade serogroups W135 and Y may now be emerging in certain countries, with serogroup A virtually disappearing. Although progress has been made in improving and coordinating the surveillance of invasive disease, the uniformity and quality of reported data reflect the fact that the current surveillance systems focus on passive rather than active reporting, hence the reliability of data may vary between countries. Consideration of vaccination policies to control meningococcal disease can only be made with a sufficient understanding of the changing epidemiology in the region.

Invasive serogroup B Neisseria meningitidis in Quebec, Canada, 2003 to 2010: persistence of the ST-269 clone since it first emerged in 2003

In the era after the introduction of the meningococcal serogroup C conjugate vaccine, from 1 January 2003 to 31 December 2010, serogroup B meningococci were the major cause of invasive meningococcal disease in the province of Québec, Canada, being responsible for 72% of all meningococcal disease cases. Of the 334 invasive serogroup B Neisseria meningitidis strains analyzed, 53.9% belonged to the ST-269 clonal complex (CC). Since it first emerged in 2003, the percentage of invasive serogroup B isolates that belonged to the ST-269 CC had increased from 35% in 2003 to 76% in 2010. Among the 180 meningococci in the ST-269 CC, 91.7% belonged to a single ST (ST-269). The most common PorA genotypes identified in the ST-269 CC were (i) VR1 19-1, VR2 15-11, VR3 36 (84%) and (ii) VR1 18-7, VR2 9, VR3 35-1 (9%). Cases of invasive disease due to the ST-269 CC were commonly found in those aged 11 to 19 years (30.5%) and 20 to 40 years (25.5%). Meningococci of the ST-269 CC were uncommon in other Canadian provinces. In contrast to the ST-269 CC, invasive serogroup B meningococci that belonged to the ST-41/44 CC were much more diverse genetically. However, one ST (ST-571), which is uncommon in the United States, accounted for 35% of all cases due to this CC. The current finding suggests that the ST-269 clone may indeed represent an emerging hypervirulent clone of meningococci.

Epidemiology of meningococcal disease in Latin America: current situation and opportunities for prevention

OBJECTIVE

Meningococcal disease continues to be a serious public health concern, being associated with high morbidity and mortality rates in many countries from Latin America. In addition to discussing recent changes in the epidemiology of meningococcal disease in the region, we also analyse the development and potential impact of new vaccines on the prevention of meningococcal disease.

METHODS

MEDLINE, SciELO, LILACS and websites of the national Ministries of Health databases were searched using the terms meningococcal disease, meningococcal epidemiology, Neisseria meningitidis, meningococcal vaccines and the name of Latin America countries, from 1998 to 2008, with emphasis on review articles, clinical trials and epidemiological studies.

RESULTS

Epidemiology of meningococcal disease in Latin America is characterized by marked differences from country to country. The overall incidence of meningococcal disease per year varied from less than 0.1 cases per 100,000 inhabitants in countries like Mexico to two cases per 100,000 inhabitants in Brazil. The highest age-specific incidence of meningococcal disease occurred in infants less than 1 year of age. Serogroups B and C were responsible for the majority of cases reported, but the emergence of serogroups W135 and Y was reported in some countries. Serogroup A disease is now rare in Latin America.

DISCUSSION

Although a few countries have established meningitis surveillance programs, the information is not uniform, and the quality of the reported data is poor in the majority of the region. The availability of new effective meningococcal conjugate vaccines and promising protein-based vaccine candidates against meningococcus B highlights the importance of a better understanding of the true burden of meningococcal disease in Latin America and also the need for cost-effectiveness studies before incorporating the new meningococcal vaccines to national immunization programs.

Vaccine preventability of meningococcal clone, Greater Aachen Region, Germany

An emerging serogroup B clone can be prevented by vaccines.

Emergence of serogroup B meningococci of clonal complex sequence type (ST) 41/44 can cause high levels of disease, as exemplified by a recent epidemic in New Zealand. Multiplication of annual incidence rates (3.1 cases/100,000 population) of meningococcal disease in a defined German region, the city of Aachen and 3 neighboring countries (Greater Aachen) prompted us to investigate and determine the source and nature of this outbreak. Using molecular typing and geographic mapping, we analyzed 1,143 strains belonging to ST41/44 complex, isolated from persons with invasive meningococcal disease over 6 years (2001–2006) from 2 German federal states (total population 26 million) and the Netherlands. A spatially slowly moving clone with multiple-locus variable-number tandem repeat analysis type 19, ST42, and antigenic profile B:P1.7–2,4:F1–5 was responsible for the outbreak. Bactericidal activity in serum samples from the New Zealand MeNZB vaccination campaign confirmed vaccine preventability. Because this globally distributed epidemic strain spreads slowly, vaccination efforts could possibly eliminate meningococcal disease in this area.

Invasive meningococcal disease in Malta: an epidemiological overview, 1994-2007

Since 1996, Malta has experienced an upsurge of invasive meningococcal disease (IMD) following an almost 30 year period with a negligible number of annually reported cases. We reviewed the 233 IMD cases notified during a 14 year period (1994-2007), and analysed epidemiological and laboratory surveillance data. The crude incidence per 100,000 inhabitants peaked in 2000 at 8.1 [95 % confidence interval (CI) 5.7-11.6] and again in 2006 at 8.9 (95 % CI 6.4-12.4), thereby placing Malta amongst the countries with the highest incidence of the disease in Europe. Of the total cases, 137 (59 %) were confirmed and 30 (13 %) were classified as probable. However, 66 cases (28 %) had no laboratory evidence of the disease and were classified as possible. Information on the serogroup was available for 114 cases. Serogroup B formed the largest proportion (76 %, n=87) followed by serogroup C (16 %, n=18). B : 4 : P1.19,15 strains (n=46) predominated throughout the study period since their first identification in 1998. With 28 deaths attributed to IMD, the overall case fatality rate was 12 %. Apart from stressing the importance of maintaining high vigilance for IMD, our findings underscore the importance of enhancing laboratory surveillance of the disease, including characterization of the meningococci. Until vaccines against a broad range of serogroup B meningococci become available for universal use, the main methods of control remain the early treatment of cases and the prevention of secondary cases.

Epidemic meningitis, meningococcaemia, and Neisseria meningitidis

Meningococcus, an obligate human bacterial pathogen, remains a worldwide and devastating cause of epidemic meningitis and sepsis. However, advances have been made in our understanding of meningococcal biology and pathogenesis, global epidemiology, transmission and carriage, host susceptibility, pathophysiology, and clinical presentations. Approaches to diagnosis, treatment, and chemoprophylaxis are now in use on the basis of these advances. Importantly, the next generation of meningococcal conjugate vaccines for serogroups A, C, Y, W-135, and broadly effective serogroup B vaccines are on the horizon, which could eliminate the organism as a major threat to human health in industrialised countries in the next decade. The crucial challenge will be effective introduction of new meningococcal vaccines into developing countries, especially in sub-Saharan Africa, where they are urgently needed.

Increased Case‐Fatality Rate Associated with Outbreaks ofNeisseria meningitidisInfection, Compared with Sporadic Meningococcal Disease, in the United States, 1994–2002

BACKGROUND

Outbreaks of meningococcal disease are infrequent but important public health events. We characterize outbreak-associated cases in the United States and compare them with sporadic disease.

METHODS

Outbreaks of meningococcal disease that occurred during the period of 1 July 1994 through 30 June 2002 were identified through state health departments, Centers for Disease Control and Prevention records, and a review of newspapers and the medical literature. Cases associated with outbreaks were compared with sporadic cases identified through population-based surveillance.

RESULTS

We identified 69 outbreaks of Neisseria meningitidis infection (median, 9.5 outbreaks per year; range, 3-14 outbreaks per year), which involved 229 patients from 30 states. Forty-three (62%) of the outbreaks involved N. meningitidis serogroup C, 17 (25%) involved serogroup B, and 9 (13%) involved serogroup Y. Twenty-five outbreaks (36%) occurred in communities, and 44 (64%) were organization based, including 12 that occurred in colleges and universities, 19 that occurred in primary and secondary schools, and 8 that occurred in nursing homes. Vaccination campaigns (with the A/C/Y/W-135 meningococcal polysaccharide vaccine) were conducted for 31 outbreaks (28 involving serogroup C and 3 involving serogroup Y). After controlling for age, serogroup, and clinical presentation, outbreak-associated cases were associated with a higher case-fatality rate than were sporadic cases (21% vs. 11%; odds ratio, 3.3; 95% confidence interval, 2.0-5.5).

CONCLUSIONS

Outbreaks remain an important but infrequent public health issue, representing <2% of all cases of meningococcal disease. However, given the increased case-fatality rate found among outbreak-related cases of N. meningitidis infection, additional investigation of factors that favor the transmission and virulence of outbreak-related strains is warranted.

A chromosomally integrated bacteriophage in invasive meningococci

Cerebrospinal meningitis is a feared disease that can cause the death of a previously healthy individual within hours. Paradoxically, the causative agent, Neisseria meningitidis, is a common inhabitant of the human nasopharynx, and as such, may be considered a normal, commensal organism. Only in a small proportion of colonized people do the bacteria invade the bloodstream, from where they can cross the blood–brain barrier to cause meningitis. Furthermore, most meningococcal disease is caused by bacteria belonging to only a few of the phylogenetic groups among the large number that constitute the population structure of this genetically variable organism. However, the genetic basis for the differences in pathogenic potential remains elusive. By performing whole genome comparisons of a large collection of meningococcal isolates of defined pathogenic potential we brought to light a meningococcal prophage present in disease-causing bacteria. The phage, of the filamentous family, excises from the chromosome and is secreted from the bacteria via the type IV pilin secretin. Therefore, this element, by spreading among the population, may promote the development of new epidemic clones of N. meningitidis that are capable of breaking the normal commensal relationship with humans and causing invasive disease.

Polysaccharide vaccines for preventing serogroup A meningococcal meningitis

BACKGROUND

Randomised trials carried out over two decades ago showed that the polysaccharide vaccine prevented serogroup A meningococcal meningitis. Subsequent non-randomised studies, however, suggested significant variations in the age-specific duration of protection among young children.

OBJECTIVES

The aim of the review was to determine the effect of polysaccharide serogroup A vaccine for preventing serogroup A meningococcal meningitis. The specific objectives were to assess the age-specific effects of the vaccine, the effect of booster doses in children under five years of age, and the duration of protection in children and adults.

SEARCH STRATEGY

In 2004, the review was updated. The following databases were searched for records of new trials: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 2004); MEDLINE (January 1966 to November Week 1 2004); and EMBASE (January 1990 to September 2004).

SELECTION CRITERIA

The first stage of the review included randomised trials. The second stage included non- randomised studies that addressed specific outcomes not answered by the randomised trials.

DATA COLLECTION AND ANALYSIS

One reviewer assessed the methodological quality of the randomised trials and two reviewers independently identified and assessed the non-randomised studies. Of the twelve eligible Randomized trials, four were excluded because of the high risk of bias in assessing vaccine efficacy. Data from the trials were pooled using the Exact method to assess vaccine efficacy at one, two and three years post vaccination. Of the 15 non-randomised studies, only two addressed the specific objectives not answered by the randomised trials but were assessed to be at high risk of bias.

MAIN RESULTS

The protective effect within the first year of vaccination was consistent across the randomised trials, and the summary vaccine efficacy was 95% (95% confidence interval (CI) 87% to 99%). Protection extended into the second and third year after vaccination but the results did not attain statistical significance. The vaccine was protective in Finnish children aged 3 months to five years. The latter was also the only trial that assessed the effect of a booster dose in children under two years of age but lacked power to yield statistically significant results. The vaccine was protective in one- to five-year old children in developing countries (Nigeria and Sudan) but the age-specific efficacy in strata between one and five years of age could not be determined.

AUTHORS' CONCLUSIONS

For the first year after vaccination, the polysaccharide serogroup A vaccine was strongly protective against serogroup A meningococcal meningitis in participants over five years of age. It was also protective beyond the first year after vaccination in this age group but the level of vaccine efficacy could not be determined with precision. Children aged one to five years in developing countries were also protected but the level of efficacy in this age group could not be determined. While the vaccine was strongly protective among children aged three months to five years in developed countries the level of efficacy across age strata within this age group could not be determined. The number of children aged under two years was too small to draw conclusions on the protective effect of a booster dose of vaccine.

Review of the cost effectiveness of immunisation strategies for the control of epidemic meningococcal meningitis

Outbreaks of meningococcal disease have caused devastation worldwide. Effective vaccines have not been used routinely, due to perceived limitations of the duration of effectiveness as well as immunogenicity when administered during infancy. Given the sporadic nature of outbreaks, the optimal use of these vaccines to control both short-term epidemic and endemic meningococcal disease has been the subject of much debate. Seven economic studies on the use of polysaccharide vaccination strategies help to highlight the relevant epidemiological and economic issues surrounding the decisions for their use. Five of these studies were based in Africa, the region where annual incidence rates can be several orders of magnitude greater than the rest of the world. These studies demonstrated that vaccination against meningococcal disease during outbreak situations is suboptimal given the inability to rapidly immunise populations in a timely fashion in resource-poor areas. However, depending on the disease incidence and the ability to deliver vaccines, the polysaccharide vaccine can be cost effective for preventive strategies when given prior to the start of outbreaks, either through presumptive vaccination or through a modified routine delivery strategy. Economic analyses of mass immunisation campaigns and modelled routine vaccination suggest that routine use of meningococcal vaccines for preventive strategies could be within the range of cost-effective public health interventions in those regions of the world where meningococcal disease is endemic. This includes the meningococcal belt of Africa, the Sahelian region.

Immunology of bacterial polysaccharide antigens

Carbohydrates in the form of capsular polysaccharides and/or lipopolysaccharides are the major components on the surface of bacteria. These molecules are important virulence factors in many bacteria isolated from infected persons. Immunity against these components confers protection against the disease. However, developing vaccines based on polysaccharides is difficult and several problems have to be solved. First of all, most of the bacterial polysaccharides are T-lymphocyte independent antigens. Anti-polysaccharide immune response is characterised by lack of T-lymphocyte memory, isotype restriction and delayed ontogeny. Children below 2 years of age and elderly respond poorly to polysaccharide antigens. Secondly, the wide structural heterogeneity among the polysaccharides within and between species is also a problem. Thirdly, some bacterial polysaccharides are poor immunogens in humans due to their structural similarities with glycolipids and glycoproteins present in man. The T-lymphocyte independent nature of a polysaccharide may be overcome by conjugating the native or depolymerised polysaccharide to a protein carrier. Such neoglycoconjugates have been proven to be efficient in inducing T-lymphocyte dependent immunity and to protect both infants as well as elderly from disease. Another approach to circumvent the T-lymphocyte independent property of polysaccharides is to select peptides mimicking the immunodominant structures. Several examples of such peptides have been described.

Correlating epidemiologic trends with the genotypes causing meningococcal disease, Maryland

Epidemic meningococcal infection is generally caused by single clones; whether nonepidemic increases in infection are clonal is unknown. We studied the molecular epidemiology of meningococcal infection during a period that the incidence increased in two age groups. Serogroup C and Y meningococcal isolates were analyzed by pulsed-field gel electrophoresis and multilocus sequence typing. From 1992 to 1999, 96.4% (27/28) of serogroup C isolates from persons 15-24 years of age were in clonal group 1, compared with 65.6% (21/32) of isolates from persons < or =14 years, and 64.3% (9/14) of isolates from adults > or =25 years (p < or = 0.01). The proportion of clonal group 2 serogroup Y strains increased from 7.7% (1/13) in 1992 to 1993 to 52.0% (13/25) in 1998 to 1999 (p < 0.01). The nonepidemic age-specific increases in serogroup C meningococcal infection in Maryland were clonal in nature and the changes in serogroup Y incidence were associated with a shift in the genotypes of strains causing invasive disease.

Development of vaccines against meningococcal disease

Neisseria meningitidis is a major cause of bacterial meningitis and sepsis. Polysaccharide-protein conjugate vaccines for prevention of group C disease have been licensed in Europe. Such vaccines for prevention of disease caused by groups A (which is associated with the greatest disease burden worldwide), Y, and W135 are being developed. However, conventional approaches to develop a vaccine for group B strains, which are responsible for most cases in Europe and the USA, have been largely unsuccessful. Capsular polysaccharide-based vaccines can elicit autoantibodies to host polysialic acid, whereas the ability of most non-capsular antigens to elicit broad-based immunity is limited by their antigenic diversity. Many new membrane proteins have been discovered during analyses of genomic sequencing data. These antigens are highly conserved and, in mice, elicit serum bactericidal antibodies, which are the serological hallmark of protective immunity in man. Therefore, there are many promising new vaccine candidates, and improved prospects for development of a broadly protective vaccine for group B disease, and for control of all meningococcal disease.

Vaccine prevention of meningococcal disease, coming soon?

The past century has seen the use of a number of vaccines for prevention and control of meningococcal disease with varied success. The use of polysaccharide vaccines for the control of outbreaks of serogroup C infections in teenagers and young adults and epidemic serogroup A disease has been established for 30 years and an effective protein-polysaccharide conjugate vaccine against serogroup C was introduced into the UK infant immunisation schedule in 2000. The next generation of these glycoconjugate vaccines will be on the shelf soon, eventually offering the prospect of eradication of serogroups A, C, Y and W135 through routine infant immunisation. Despite these exciting prospects, serogroup B meningococci still account for a majority of infections in industrialised nations but development of safe, immunogenic and effective serogroup B meningococcal vaccines has been an elusive goal. Outer membrane vesicle vaccines for B disease are already used in some countries, and will likely be used more widely in the next few years, but efficacy for endemic disease in children has so far been disappointing. However, the innovations arising from the availability of the meningococcal genome sequence, public and scientific interest in the disease and recent pharmaceutical company investment in development of serogroup B vaccines may have started the countdown to the end of meningococcal infection in children.

[Shared surveillance: meningococcal disease vs influenza]

OBJECTIVE

To analyse the association between the behavior of meningococcal disease and influenza, using for this purpose population statistics for Spain for the period of 1964 to 1997.

METHODS

Ecological study of the incidence of meningococcal disease and influenza in Spain from 1964 to 1997, inclusive. The study used weekly statistical data for these diseases supplied by the Compulsory Disease Reporting System (Enfermedades de Declaración Obligatoria, EDO). The deterministic component of the meningococcal disease and influenza series was studied by means of spectral analysis based on the Fast Fourier Transformation, and the non-deterministic component was studied using the ARIMA model. The Box-Jenkins method was used for pre-bleaching the series, and a cross-correlation was subsequently established between the residuals in order to detect the presence of any significant correlations between the meningococcal disease and influenza series.

RESULTS

During the period from 1964 to 1997, the week that showed, on average, the greatest number of cases for the season was week 7 in the case of meningococcal disease and week 6 in the case of influenza. Spectral analysis of the meningococcal disease and influenza series clearly demonstrated the annual periodicity of both series, and periodicity of nearly 11 years for meningococcal disease and slightly over 10 years for influenza. When cross-correlation is established after prebleaching the series, positive correlations are obtained in the results of lags 0, 1, 2, and 3. Introducing influenza as an exogenous variable in the multivariate model of meningococcal disease corroborates these results. There was a statistically significant relationship between the two processes during the same week and with a three-week lapse.

CONCLUSIONS

By means of a methodology not previously applied to this subject, and by the use of prolonged time-span, country-comprehensive population statistics (which includes several epidemics waves), an association was shown to exist between meningococcal disease and influenza. This suggests the need for the surveillance of the two processes in an interrelated manner.

Preventing meningococcal infection in college students

The incidence of invasive meningococcal disease in adolescents and young adults of high school and college age has recently increased in the United States. Recent studies indicate that certain groups of college students are at increased risk. This has led to the recent Advisory Committee Immunization Practices recommendation that college freshman dormitory residents be provided information about meningococcal infection and the benefits of vaccination. Future studies will need to focus on the potential vaccine prevention of the increased risk of meningococcal infection in persons of high school age, particularly as new conjugate meningococcal vaccines become available.

Update on meningococcal disease with emphasis on pathogenesis and clinical management

The only natural reservoir of Neisseria meningitidis is the human nasopharyngeal mucosa. Depending on age, climate, country, socioeconomic status, and other factors, approximately 10% of the human population harbors meningococci in the nose. However, invasive disease is relatively rare, as it occurs only when the following conditions are fulfilled: (i) contact with a virulent strain, (ii) colonization by that strain, (iii) penetration of the bacterium through the mucosa, and (iv) survival and eventually outgrowth of the meningococcus in the bloodstream. When the meningococcus has reached the bloodstream and specific antibodies are absent, as is the case for young children or after introduction of a new strain in a population, the ultimate outgrowth depends on the efficacy of the innate immune response. Massive outgrowth leads within 12 h to fulminant meningococcal sepsis (FMS), characterized by high intravascular concentrations of endotoxin that set free high concentrations of proinflammatory mediators. These mediators belonging to the complement system, the contact system, the fibrinolytic system, and the cytokine system induce shock and diffuse intravascular coagulation. FMS can be fatal within 24 h, often before signs of meningitis have developed. In spite of the increasing possibilities for treatment in intensive care units, the mortality rate of FMS is still 30%. When the outgrowth of meningococci in the bloodstream is impeded, seeding of bacteria in the subarachnoidal compartment may lead to overt meningitis within 24 to 36 h. With appropriate antibiotics and good clinical surveillance, the mortality rate of this form of invasive disease is 1 to 2%. The overall mortality rate of meningococcal disease can only be reduced when patients without meningitis, i.e., those who may develop FMS, are recognized early. This means that the fundamental nature of the disease as a meningococcus septicemia deserves more attention.

Update on meningococcal disease with emphasis on pathogenesis and clinical management

The only natural reservoir of Neisseria meningitidis is the human nasopharyngeal mucosa. Depending on age, climate, country, socioeconomic status, and other factors, approximately 10% of the human population harbors meningococci in the nose. However, invasive disease is relatively rare, as it occurs only when the following conditions are fulfilled: (i) contact with a virulent strain, (ii) colonization by that strain, (iii) penetration of the bacterium through the mucosa, and (iv) survival and eventually outgrowth of the meningococcus in the bloodstream. When the meningococcus has reached the bloodstream and specific antibodies are absent, as is the case for young children or after introduction of a new strain in a population, the ultimate outgrowth depends on the efficacy of the innate immune response. Massive outgrowth leads within 12 h to fulminant meningococcal sepsis (FMS), characterized by high intravascular concentrations of endotoxin that set free high concentrations of proinflammatory mediators. These mediators belonging to the complement system, the contact system, the fibrinolytic system, and the cytokine system induce shock and diffuse intravascular coagulation. FMS can be fatal within 24 h, often before signs of meningitis have developed. In spite of the increasing possibilities for treatment in intensive care units, the mortality rate of FMS is still 30%. When the outgrowth of meningococci in the bloodstream is impeded, seeding of bacteria in the subarachnoidal compartment may lead to overt meningitis within 24 to 36 h. With appropriate antibiotics and good clinical surveillance, the mortality rate of this form of invasive disease is 1 to 2%. The overall mortality rate of meningococcal disease can only be reduced when patients without meningitis, i.e., those who may develop FMS, are recognized early. This means that the fundamental nature of the disease as a meningococcus septicemia deserves more attention.

Polysaccharide vaccines for preventing serogroup A meningococcal meningitis

BACKGROUND

Controlled trials over two decades ago showed that the polysaccharide vaccine prevented meningococcal meningitis. Subsequent observational studies suggested variations in the level and duration of protection, particularly among young children.

OBJECTIVES

To determine the effect of polysaccharide serogroup A vaccine for preventing serogroup A meningococcal meningitis.

SEARCH STRATEGY

MEDLINE and the Cochrane Controlled Trials Register.

SELECTION CRITERIA

Randomised and other prospective controlled trials.

DATA COLLECTION AND ANALYSIS

One reviewer collected data and assessed the methodologic quality of the trials. Data were pooled using the Exact method to assess vaccine efficacy at one, two and three years post-vaccination.

MAIN RESULTS

The protective effect within the first year was consistent across all eight trials, including one with participants exclusively under six years of age (in Finland); overall vaccine efficacy was 95% (Exact 95% CI 87%, 99%). The Finnish trial lacked statistical power to assess the effect of a booster dose given to children less than 18 months old. In the three other trials that included children less than six years old (one in Sudan and two in Nigeria), none of the vaccinated children developed meningitis, but the statistical significance of this finding was undetermined. Protection extended into the second (in two studies) and third (in one study) years after vaccination, but these results were also not statistically significant.

REVIEWER'S CONCLUSIONS

When compared with current recommendations, the methodological quality and relative incompleteness of the published reports could arguably render the trials invalid for this review. However, it was unlikely that the results of the trials in such diverse settings would have been biased towards a strong and consistent protective effect. Immunogenicity trials were not included in this review. Stage two of the review will assess the vaccine effect from observational studies.

Polyosides (encapsulated bacteria)

The polysaccharide capsule which surrounds bacterial species such as Haemophilus influenzae, Streptococcus pneumoniae, Neisseria meningitidis and Salmonella typhi is a potent virulence factor by protecting the bacteria from phagocytosis. The host responds with antibody production and specific antibodies plus complement binding to the capsule facilitate opsonization of the micro-organism, which is phagocytized and eliminated. Purified capsular polysaccharides elicit T-independent antibody responses without a memory function, but are often poorly immunogenic in infants where much of the invasive H. influenzae type b (Hib) and pneumococcal infections is seen. Therefore purified polysaccharides have found limited use as vaccines. However, covalent linkage of the capsular polysaccharide, or fractions thereof, to immunogenic carrier proteins creates glycoconjugates which are T-dependent antigens and which elicit antibodies also in infants and which prime for boosting either with the glycoconjugate or the capsular polysaccharide. In the last decade Hib glycoconjugate vaccines have been successfully introduced and in countries with very high immunization coverage the disease has been virtually eliminated and a decline of over 95% has been seen in countries with slightly lower vaccine rates. World-wide use of Hib glycoconjugate vaccines offers the possibility of elimination of invasive Hib disease. Pneumococcal (11 serotypes with coverage of approximately 85% of invasive disease), meningococcal (A, C, W 135, Y but not B) and S. typhi glycoconjugates are in advanced development and offer the prospect of being as successful as the Hib glycoconjugates.

Glycoprotein conjugate vaccines

The polysaccharide capsule which surrounds bacterial species like Haemophilus influenzae, Streptococcus pneumoniae, Neisseria meningitidis, Salmonella typhi, is a potent virulence factor. It protects the bacterium from phagocytosis, but capsule specific antibodies plus complement binding to the capsule opsonise the organism for phagocytosis and elimination. Purified capsules elicit T-independent antibody responses without a memory function, and are often poorly immunogenic in infants where much of invasive H. influenzae type b (Hib) and pneumococcal infection is seen. Covalent linkage of the polysaccharide, or fractions thereof, to immunogenic carrier proteins creates glycoconjugates which are T-dependent antigens and which prime for boosting either with the glycoconjugate or the capsular polysaccharide; During the 1990s, four Hib glycoconjugate vaccines have been introduced and in countries that have vaccinated the majority of children, the success has been stunning. In countries with very high immunization coverage the disease has been virtually eliminated and, to a decline of over 95% in countries with slightly lower vaccine rates. Worldwide use of Hib glycoconjugate vaccines offers the possibility of elimination of invasive Hib disease. Pneumococcal (11 serotypes with coverage of approximately 85% of invasive disease) and meningococcal (A, C, W 135, Y but not B) glycoconjugates are in pre-registration phases and offer the prospect of being as successful as the Hib glycoconjugates.

Prophylaxis of bacterial meningitis

A comprehensive review of all major agents causing bacterial meningitis--meningococcus of the groups A, B, C, W135, and Y, pneumococcus, and Haemophilus influenzae type B (Hib)--is done in terms of preventing them by chemoprophylaxis or vaccination. Some evidence suggests that the group B meningococcal disease may also be very likely preventable by a vaccine that is already available. Excellent Hib conjugates use a technique that is expected to revolutionize immunoprophylaxis against most meningococcal and pneumococcal diseases in the near future. Unfortunately, the high cost of conjugate vaccines restricts their use in many poor countries.

[Meningococcal C disease epidemic in Galicia 1996: the decision making process]

In this article we describe the decision making process used to choose the best alternative for bringing under control an epidemic of meningococcal C disease, which occurred in Galicia in 1996. In the decision making process, we used a methodology which consisted on the identification and definition of a problem, in order to identify alternative solutions and to select one, and finally implement and evaluate it. The health problem was detected studying the data obtained from a survey conducted following an outbreak of meningococcal C disease in february 1995 and from the active epidemiological surveillance system created thereafter. Because this was a new, complex and severe problem, with far-reaching social consequences, critical for our organization, and with long-term implications, and because it was considered important to take the decision as objectively as possible and to clearly explain it, the methodology chosen to solve the problem was a non-programmed, multicriteria making decision process, carried out by a working group using a criterion weighting approach. This working group was created within the General Directorate of Public Health, composed of specialist and of people responsible for the different areas involved. The working group put into practice the different steps of the methodology. The assessment criteria and their respective weights were: effect (efficacy measured by the number of cases we could have prevented if the alternatives were applied in the previous season) 40%; cost (in millions of pesetas) 15%; acceptability (acceptance of and response to each strategy from different groups: general population, health care professionals, other Administrations with competency in Public Health) 30%; and coherence (adherence to the currently accepted strategies for disease control in other countries)15%. When these criteria were applied to the ten alternatives considered, a score was obtained for each one of them. The highest scoring alternative corresponded to the massive vaccination of the total population of Galicia between 18 months and 19 years of age.

[Meningococcal disease: epidemiology and control of secondary cases]

Epidemiological features of meningococcal disease described as from the second half of the 80's inclusive, have motivated a revision of current guidelines for sporadic disease and outbreak control. The increase of disease among teenagers and linked cases involving schools are the two most significant aspects that have prompted the revision of control measures. Vaccination routines and advice for the disease management of clusters are also relevant features recently revised. This present paper describes the management and some epidemiological features of secondary cases.

[Analysis of the management of the vaccination campaign in 1996-1997 against meningococcus C in Galicia]

This paper describes the process to design and plan a vaccination campaign against group C N. Meningitidis developed in the Autonomous Community of Galicia between December 9, 1996 and January 31, 1997. We also analyse the results of this process in terms of management results, vaccine coverage and preliminary estimates of effectiveness. A Work group was established, made up of professionals in charge of different intervention areas. A person was designated in charge of the whole campaign and a follow-up and information system was created. The work plan consisted of daily meetings for follow-up, co-ordination and task distribution; and periodical meetings with primary health care and peripheral public health coordinators. Strategies of implantation--in order to make sure the campaign accessibility and acceptability; of budget and of communication with health workers, inhabitants and mass media were developed. Up to 100 tasks were identified to develop the technical information and logistic activities: mailings, meetings, leaflets, ...; purchasing of 584.980 doses of vaccine, supplying to 715 vaccination points (1040 deliveries); problem solving and intervention recording. A vaccination coverage of 85% was achieved, with notification of 8 adverse reactions and 6 errors in the administration of the vaccine (34 children affected). The strategy chosen for the design and planning of the campaign has proven to be effective and valid and sufficient to achieve the final goals, in due time and without problems of misinformation, shortage of vaccine or lack of participation of professionals or people. Mistakes due to incorrect administration of the vaccine, management problems, rupture of the cold chain or recording failures were minimal and accidental.

Acute meningococcal meningitis: analysis of features of the disease according to the age of 255 patients. Copenhagen Meningitis Study Group

Clinical and laboratory features of acute meningococcal meningitis according to age were studied in 255 patients. Whereas males accounted for three out of five patients aged 0-4 years, females accounted for three out of four patients older than 50 years of age. All patients had clinical signs of nuchal rigidity and fever. Patients older than 30 years of age had less frequent petechiae (62%) than younger patients (81%). Furthermore, elderly patients above 50 years of age were prone to an obtunded mental state and a prolonged disease course with fever. Without relation to age, 2/3 had purulent meningitis and 2/3 had marked peripheral leucocytosis (> 15 x 10(9) cells/l); 90% of patients had at least one of these findings. The cellular inflammatory response in peripheral blood indicated a bacterial aetiology in > 95% of the cases. More than 80% of children and adults had abnormal CSF biochemical findings, but the level of protein and the glucose ratio (CSF/serum) were positively and negatively correlated to increasing age of the patient, respectively: thus, in children these biochemical markers may be unreliable in the differentiation between a bacterial and non-bacterial aetiology. Thrombocytopenia (< 100.000 x 10(9)/I) was not associated with age, though the lowest platelet count was found in elderly patients. The case fatality rate was 7.5%, but neither age, sex nor sign of septicaemia was associated with fatality. Thrombocytopenia, a lowered coagulation index (< 0.5, factors II, VII, X), a moderate anaemia (haemoglobin < 11 g/dl), an obtunded mental state and a history of convulsions were poor prognostic factors; only anaemia was independently correlated to fatality so this should be considered as an important prognostic marker in the acute phase of meningococcal meningitis.

The 1990 meningococcal meningitis epidemic of Sarh (Chad): how useful was an earlier mass vaccination?

A large outbreak of meningococcal meningitis (Serogroup A) occurred in southern Chad in 1990. We describe the epidemic in the town of Sarh, where a mass vaccination against meningococcal meningitis had taken place two years before, in 1988 (estimated coverage: 66%). Early warning that an epidemic was imminent was given at the end of February, following more than 15 recorded cases per 100,000 population on 3 consecutive weeks. This threshold proved to be adequate to predict the outbreak. A total of 721 cases were recorded at Sarh hospital and at a nearby health centre. Direct agglutination tests confirmed that Neisseria meningitis serogroup A was the only causative agent. The overall incidence rate in this population of 80,000 was 0.9%. The highest weekly incidence rate was 186 cases per 100,000 population. The mean age of the patients was 12.6 years and age-specific incidence rates ranged from 0.23% to 1.42%. The male/female sex ratio was 1.36. Overall, the mortality among hospitalized patients was 7.9%. Mortality increased during the epidemic. The major risk factor for dying was the delay until reaching hospital. Only 4 out of 29 interviewed parents said that their child had been vaccinated two years before. Among adult patients this proportion was 12/38 (32%). Because of the small numbers and because of the impossibility to check the vaccination records it was not possible to assess precisely the impact of earlier mass vaccination. However, the previous mass vaccination did not prevent this major epidemic and its impact is likely to have been unimportant.

[Occurrence of meningococcal meningitis in a Southern region of Brazil, from 1974 to 1980, using the point event model]

Descriptive statistical techniques and point event model methods were used to investigate the temporal series of cases of meningococcal meningitis which occurred in 100 municipalities in the Rio Grande do Sul State, Brazil, during the period 1974-1980. The data were grouped by epidemiological state (epidemic or endemic), and separated into 5 groups according to the municipal population. The number of cases of the disease notified weekly was analysed by means of incidence coefficients, with the purpose of studying the epidemic threshold for the state. The time interval between events was analysed in the light of their probability density functions and expected density functions, with the objective of studying the relationship and dependences among events. The analysis of the epidemic threshold suggests that there should not be only one threshold value for detection of outbreak of the disease throughout the state. Analysis of the expected density function extracted from inter-event intervals of the epidemic state showed a correlational structure indicating dependence between events occurring up to 14 weeks apart. No significant correlation for the endemic state, taking as reference model the shuffled version of the original intervals, was observed.

Clinical features and complications of epidemic group A meningococcal disease in Sudanese children

The clinical presentation and laboratory features in relation to short-term outcome in 118 prospectively studied Sudanese children who were admitted with meningococcal (MC) meningitis and/or septicaemia during the 1988 group A MC epidemic in Greater Khartoum are described. Their ages ranged from 25 days to 15 years (mean: 78 months) and 42% were less than 5 years old. The male:female ratio was 1.6:1. Forty (34%) came from one of the peri-urban shanty towns encircling Greater Khartoum. A history of MC immunization (A and C vaccine) was obtained in 22%, but only five children (4.8%) had the vaccine between 4 weeks and 1 year before their illness. The commonest symptoms on admission were vomiting, neck rigidity and diarrhoea. Convulsions were significantly more frequent in children under 5 years old (p = 0.0005). Fifty-six (47%) had evidence of malnutrition. In descending order, fever, neck stiffness and Kernig's sign were the most commonly observed signs, the latter two being significantly more often detected in children older than 1 year. Twenty-four patients 20%) had disturbed consciousness. The case fatality rate was 6.3% and this was significantly higher in those presenting with meningococcal septicaemia (p = 0.0006). Other significant associations with mortality were short duration (less than 1 day) of symptoms (p = 0.0006) and clinical shock detected on admission p = 0.003). Transient complications were infrequent and permanent neurological sequelae were confined to bilateral profound sensorineural hearing loss in three children (2.9%) and hemiplegia in two 1.9%.(ABSTRACT TRUNCATED AT 250 WORDS)

Features of a large epidemic of group A meningococcal meningitis in Khartoum, Sudan in 1988

A large epidemic (February-August 1988) of group A sulphonamide resistant, clone III-1 meningococcal meningitis in Khartoum, Sudan is described. A total of 10,099 cases were admitted to treatment centers with 8,397 cases during March and April, corresponding to an annual incidence of 1,679/100,000 inhabitants during this period. The age profile showed a high morbidity in adults (31% of the cases greater than or equal to 20 years). The male dominance was marked especially in the adult cases with a proportion of 3.2:1. The epidemic started during the hot and dry season and declined when the clouds came, humidity rose, temperature fell and a mass vaccination campaign had been implemented together with other epidemic precautions. Vaccination with a combined group A/C polysaccharide vaccine had been given 4 weeks-1 year before hospitalization to 11% of the children, 80% of whom were greater than 18 months of age. The estimated case fatality rate was 6.3%. Since 47% of the cases came from periurban and rural areas, the actual mortality during the epidemic might have been higher when considering those who may have died before reaching any of the treatment centres. Fatal cases had a short history of acute illness and a septic condition. Septicaemia was rare and seen in only 3.7% of the cases, the rest had acute purulent meningitis. Hearing loss/impairment and hemiplegia was diagnosed in 2-3% of the cases. The epidemiology, based on detailed typing/subtyping and restriction enzyme patterns of meningococcal strains, was apparently associated with the Mecca outbreak in August 1987.