Hajj-associated outbreak strain of Neisseria meningitidis serogroup W135: estimates of the attack rate in a defined population and the risk of invasive disease developing in carriers

Public Health Preparedness for the World's Largest Mass Gathering: 2010 World Exposition in Shanghai, China

The 2010 World Exposition in Shanghai China (Expo) was the largest mass gathering in world history, attracting a record 72 million visitors. More than 190 countries participated in the Expo, along with more than 50 international organizations. The 2010 Expo was six months in duration (May 1 through October 30, 2010), and the size of the venue site comprised 5.28 square kilometers. Great challenges were imposed on the public health system in Shanghai due to the high number and density of visitors, long duration of the event, and other risk factors such as high temperatures, typhoon, etc.

As the major metropolitan public health agency in Shanghai, the Shanghai Municipal Center for Disease Control and Prevention (SCDC) implemented a series of actions in preparing for, and responding to, the potential health impact of the world's largest mass gathering to date, which included partnerships for capacity building, enhancement of internal organizational structure, risk assessment, strengthened surveillance, disaster planning and exercises, laboratory management, vaccination campaign, health education, health intervention, risk communication and mass media surveillance, and technical support for health inspection. The clear-cut organizational structures and job responsibilities, as well as comprehensive operational and scientific preparations, were key elements to ensure the success of the 2010 World Exposition.

YiH, Zheng'anY, FanW, XiangG, ChenD, YongchaoH, XiaodongS, HaoP, MahanyM, KeimM. Public health preparedness for the world's largest mass gathering: 2010 World Exposition in Shanghai, China. Prehosp Disaster Med. 2012;27(6):1-6.

The spread of vaccine-preventable diseases by international travellers: a public-health concern

Vaccine-preventable diseases (VPDs) are costly at both the individual and societal levels. The most common VPDs recorded in travellers are enteric (typhoid or paratyphoid B) fever, acute viral hepatitis, influenza, varicella, measles, pertussis and bacterial meningitis. Travellers suffering from VPDs are frequently hospitalized, illustrating the point that VPDs are serious and expensive. Many travellers are not properly immunized before travel. In addition to individual consequences, VPDs can have public-health consequences if they are introduced or re-introduced by infected travellers returning to areas with susceptible populations. The international spread of poliomyelitis, Neisseria meningitidis serogroup W135 meningococcal infections, measles and influenza provides strong evidence of the role of international travel in the globalization of VPDs. The surveillance of the emergence, re-emergence or spread of VPDs is essential to adapt pre-travel advice and the responses to the VPD.

The investigational meningococcal serogroups A, C, W-135, Y tetanus toxoid conjugate vaccine (ACWY-TT) and the seasonal influenza virus vaccine are immunogenic and well-tolerated when co-administered in adults

Co-administration of meningococcal serogroups A, C, W-135 and Y conjugate vaccine (ACWY-TT) with seasonal influenza vaccine was investigated in a subset of adults enrolled in a larger study evaluating lot-to-lot consistency of ACWY-TT and non-inferiority to licensed tetravalent meningococcal polysaccharide vaccine (MenPS). Subjects in this sub-study were randomized (3:1:1) to receive ACWY-TT alone (ACWY-TT group) or with seasonal influenza vaccine (Coad), or licensed MenPS alone. Serum bactericidal antibodies (rSBA) and serum haemagglutination-inhibition (HI) antibody titers were measured pre- and 1 mo post-vaccination. Non-inferiority of the Coad group compared with ACWY-TT group was demonstrated in terms of rSBA geometric mean antibody titers (GMTs) to serogroups A, W-135 and Y. For serogroup C the pre-defined non-inferiority limit was marginally exceeded. Post-vaccination rSBA GMTs were significantly higher (exploratory analysis) in the Coad group compared with the MenPS group for serogroups A, W-135, and Y and were similar to the MenPS group for serogroup C. Overall, > 97% of subjects achieved rSBA titers ≥ 1:128 for all serogroups. The Coad group met all criteria defined by the Committee on Human Medicinal Products (CHMP) for seroprotection, seroconversion and seroconversion factor for HI antibodies for all three influenza strains. Grade 3 solicited local/general symptoms were reported by ≤ 1.9% of subjects in any group. These data support the co-administration of ACWY-TT with seasonal influenza vaccine when protection is needed against both diseases.

 

This study is registered at clinicaltrials.gov NCT00453986

The immunogenicity and safety of an investigational meningococcal serogroups A, C, W-135, Y tetanus toxoid conjugate vaccine (ACWY-TT) compared with a licensed meningococcal tetravalent polysaccharide vaccine: a randomized, controlled non-inferiority study

Immunogenicity and safety of ACWY-TT compared with licensed ACWY polysaccharide vaccine (MenPS) in healthy adults, and lot-to-lot consistency of three ACWY-TT lots were evaluated in a phase 3, open, controlled study. Adults aged 18–55 y were randomized to receive ACWY-TT (one of three lots) or MenPS. Serum bactericidal antibodies (rSBA) were measured pre- and 1 mo post-vaccination. Adverse events (AEs) were assessed 4 d (solicited symptoms) and 31 d (unsolicited symptoms) post-vaccination. Serious AEs were reported up to 6 mo after vaccination. The number of vaccinated subjects was 1247 (ACWY-TT, n = 935; MenPS, n = 312). ACWY-TT lot-to-lot consistency and non-inferiority of ACWY-TT as compared with MenPS groups were demonstrated according to pre-specified criteria. The percentages of subjects with a vaccine response (VR = rSBA titer ≥ 1:32 in initially seronegative; ≥ 4-fold increase in initially seropositive) to ACWY-TT vs. MenPS were 80.1%/69.8% (serogroup A), 91.5%/ 92.0% (C), 90.2%/85.5% (W-135), 87.0%/78.8% (Y). Exploratory analyses showed that for serogroups A, W-135 and Y, VR rates and GMTs were significantly higher for ACWY-TT compared with MenPS. For each serogroup, ≥ 98.0% of subjects had rSBA titers ≥ 1:128. Grade 3 solicited AEs were reported in ≤ 1.6% of subjects in any group. The immunogenicity of ACWY-TT vaccine was non-inferior to MenPS for all four serogroups in adults, with significantly higher VR rates to serogroups A, W-135 and Y and an acceptable safety profile. Consistency of 3 ACWY-TT production lots was demonstrated. These data suggest that, if licensed, ACWY-TT conjugate vaccine may be used for protection against invasive meningococcal disease in healthy adults.

 

This study is registered at clinicaltrials.gov NCT00453986

Epidemiology and prevention of meningococcal disease: a critical appraisal of vaccine policies

Meningococcal disease is characterized by a marked variation in incidence and serogroup distribution by region and over time. In several European countries, Canada and Australia, immunization programs, including universal vaccination of infants or toddlers with catch-up campaigns in children and adolescents, aimed at controlling disease caused by meningococcal serogroup C have been successful in reducing disease incidence through direct and indirect protection. More recently, meningococcal conjugate vaccines targeting disease caused by serogroups A, C, W-135 and Y have been licensed and are being used in adolescent programs in the USA and Canada while a mass immunization campaign against serogroup A disease has been implemented in Africa. Positive results from clinical trials using vaccines against serogroup B disease in various age groups suggest the possibility of providing broader protection against serogroup B disease than is provided by the currently used outer membrane vesicle vaccines. The purpose of our review of meningococcal epidemiology and assessment of existing policies is to set the stage for future policy decisions. Vaccination policies to prevent meningococcal disease in different regions of the world should be based on quality information from enhanced surveillance systems.

Global perspectives for prevention of infectious diseases associated with mass gatherings

We assess risks of communicable diseases that are associated with mass gatherings (MGs), outline approaches to risk assessment and mitigation, and draw attention to some key challenges encountered by organisers and participants. Crowding and lack of sanitation at MGs can lead to the emergence of infectious diseases, and rapid population movement can spread them across the world. Many infections pose huge challenges to planners of MGs; however, these events also provide an opportunity to engage in public health action that will benefit host communities and the countries from which participants originate.

Neisseria meningitidis: biology, microbiology, and epidemiology

Neisseria meningitidis (the meningococcus) causes significant morbidity and mortality in children and young adults worldwide through epidemic or sporadic meningitis and/or septicemia. In this review, we describe the biology, microbiology, and epidemiology of this exclusive human pathogen. N.meningitidis is a fastidious, encapsulated, aerobic gram-negative diplococcus. Colonies are positive by the oxidase test and most strains utilize maltose. The phenotypic classification of meningococci, based on structural differences in capsular polysaccharide, lipooligosaccharide (LOS) and outer membrane proteins, is now complemented by genome sequence typing (ST). The epidemiological profile of N. meningitidis is variable in different populations and over time and virulence of the meningococcus is based on a transformable/plastic genome and expression of certain capsular polysaccharides (serogroups A, B, C, W-135, Y and X) and non-capsular antigens. N. meningitidis colonizes mucosal surfaces using a multifactorial process involving pili, twitching motility, LOS, opacity associated, and other surface proteins. Certain clonal groups have an increased capacity to gain access to the blood, evade innate immune responses, multiply, and cause systemic disease. Although new vaccines hold great promise, meningococcal infection continues to be reported in both developed and developing countries, where universal vaccine coverage is absent and antibiotic resistance increasingly more common.

Effects of multi-walled carbon nanotubes (MWCNT) under Neisseria meningitidis transformation process

Background

This study aimed at verifying the action of multi-walled carbon nanotubes (MWCNT) under the naturally transformable Neisseria meningitidis against two different DNA obtained from isogenic mutants of this microorganism, an important pathogen implicated in the genetic horizontal transfer of DNA, causing the escape of the principal vaccination measured worldwide by the capsular switching process.

Materials and methods

The bacterium receptor strain C2135 was cultivated and had its mutant DNA donor M2 and M6, which received a receptor strain and MWCNT at three different concentrations. The inhibition effect of DNAse on the DNA in contact with nanoparticles was evaluated.

Results

The results indicated an in increase in the transformation capacity of N. meninigtidis in different concentrations of MWCNT when compared with negative control without nanotubes. A final analysis of the interaction between DNA and MWCNT was carried out using Raman Spectroscopy.

Conclusion

These increases in the transformation capacity mediated by MWCNT, in meningococci, indicate the interaction of these particles with the virulence acquisition of these bacteria, as well as with the increase in the vaccination escape process.

Meningococcal disease in Asia: an under-recognized public health burden

A literature search traced existing information on meningococcal disease in Asia. Reviewed data describing the epidemiology of meningococcal disease in Asia are incomplete, due in part to absence of surveillance in many countries, poor bacterial detection methods and social and healthcare barriers to disease reporting. This suggests that meningococcal disease in some Asian countries may be under-recognized, with a need to introduce/improve existing surveillance and case identification systems. Nevertheless, in some developing Asian countries, the disease burden may be significant. Serogroup A meningococcal epidemics are responsible for high morbidity and mortality in some countries and continue to be an ongoing threat, particularly in developing countries. There is an increasing role played by serogroups C, Y, and W-135 in invasive disease, indicating evolving meningococcal disease epidemiology in some countries. Multivalent meningococcal conjugate vaccines offer new opportunities in the region for reducing the meningococcal disease burden.

Immunogenicity of a single dose of tetravalent meningococcal serogroups A, C, W-135, and Y conjugate vaccine administered to 2- to 10-year-olds is noninferior to a licensed-ACWY polysaccharide vaccine with an acceptable safety profile

BACKGROUND

Meningococcal disease remains an important cause of invasive bacterial infections in children less than 5 years of age. Immunogenicity and safety of the investigational ACWY vaccine conjugated with tetanus toxoid (ACWY-TT, GlaxoSmithKline Biologicals) were evaluated in 1501 healthy 2- to 10-year-old children in the Philippines, India, Lebanon, and Saudi Arabia.

METHODS

Children were randomized (3:1) to receive ACWY-TT or licensed tetravalent meningococcal polysaccharide vaccine (Mencevax, GlaxoSmithKline, Men-PS). Diary cards were used to collect solicited symptoms for 4 days after vaccination. Serious adverse events were reported for 6 months. Serum bactericidal activity (rSBA, rabbit complement) was measured before and 1 month after vaccination in the first 75% of subjects enrolled in each country.

RESULTS

The statistical criteria for noninferiority in terms of rSBA vaccine responses were reached. Exploratory analyses showed that postvaccination rSBA titers ≥ 1:8 and ≥ 1:128 were significantly higher after ACWY-TT than Men-PS for serogroups C, W-135, and Y, and rSBA vaccine responses and geometric mean antibody titers were significantly higher for all 4 serogroups after administration of ACWY-TT. Noninferiority in terms of incidences of grade 3 general symptoms was not demonstrated. ACWY-TT was well tolerated with grade 3 events reported in <1% of subjects per group. No serious adverse events were considered related to vaccination.

CONCLUSION

ACWY-TT was immunogenic in children between 2 to 10 years of age with a clinically acceptable safety profile that resembled licensed Men-PS. These data support a positive benefit/risk ratio for the ACWY-TT vaccine.

The Global Meningococcal Initiative: recommendations for reducing the global burden of meningococcal disease

The Global Meningococcal Initiative (GMI) is composed of an international group of scientists, clinicians and public health officials with expertise in meningococcal immunology, epidemiology and prevention. The primary goal of the GMI is the promotion of the global prevention of invasive meningococcal disease through education and research. The GMI members reviewed global meningococcal disease epidemiology, immunization strategies, and research needs. Over the past decade, substantial advances in meningococcal vaccine development have occurred and much has been learned about prevention from countries that have incorporated meningococcal vaccines into their immunization programs. The burden of meningococcal disease is unknown for many parts of the world because of inadequate surveillance, which severely hampers evidence-based immunization policy. As the field of meningococcal vaccine development advances, global surveillance for meningococcal disease needs to be strengthened in many regions of the world. For countries with meningococcal vaccination policies, research on vaccine effectiveness and impact, including indirect effects, is crucial for informing policy decisions. Each country needs to tailor meningococcal vaccination policy according to individual country needs and knowledge of disease burden. Innovative approaches are needed to introduce and sustain meningococcal vaccination programs in resource-poor settings with a high incidence of meningococcal disease.

Consensus building and recommendations based on the available epidemiology of meningococcal disease in Gulf Cooperation Council States

The Gulf Cooperation Council (GCC) States share concerns about meningococcal disease, particularly in association with the Hajj and Umrah pilgrimages, which have been connected with outbreaks within the Kingdom of Saudi Arabia and among contacts of the pilgrims in their countries of origin. Currently, the most prevalent meningococcal serogroup in the GCC States is W-135. Although vaccination with polysaccharide vaccines has protected pilgrims and their close contacts from invasive disease, the potential availability of novel conjugate vaccines, such as the one currently used for vaccination of military personnel in the Kingdom of Saudi Arabia, prompted an evaluation of disease epidemiology in the region. For several countries, published data on recent epidemiology are not available. We report findings from a meeting of the GCC States Meningitis Study Group, which comprised experts from the Kingdom of Saudi Arabia, the Kingdom of Bahrain, Kuwait, Qatar, the Sultanate of Oman, and the United Arab Emirates. These experts provided an update on epidemiology and current vaccination practices in the GCC States, and discussed new approaches to more effective disease prevention.

Epidemiology, diagnosis, and antimicrobial treatment of acute bacterial meningitis

The epidemiology of bacterial meningitis has changed as a result of the widespread use of conjugate vaccines and preventive antimicrobial treatment of pregnant women. Given the significant morbidity and mortality associated with bacterial meningitis, accurate information is necessary regarding the important etiological agents and populations at risk to ascertain public health measures and ensure appropriate management. In this review, we describe the changing epidemiology of bacterial meningitis in the United States and throughout the world by reviewing the global changes in etiological agents followed by specific microorganism data on the impact of the development and widespread use of conjugate vaccines. We provide recommendations for empirical antimicrobial and adjunctive treatments for clinical subgroups and review available laboratory methods in making the etiological diagnosis of bacterial meningitis. Finally, we summarize risk factors, clinical features, and microbiological diagnostics for the specific bacteria causing this disease.

Global public health implications of a mass gathering in Mecca, Saudi Arabia during the midst of an influenza pandemic

BACKGROUND

Every year millions of pilgrims from around the world gather under extremely crowded conditions in Mecca, Saudi Arabia to perform the Hajj. In 2009, the Hajj coincided with influenza season during the midst of an influenza A (H1N1) pandemic. After the Hajj, resource-limited countries with large numbers of traveling pilgrims could be vulnerable, given their limited ability to purchase H1N1 vaccine and capacity to respond to a possible wave of H1N1 introduced via returning pilgrims.

METHODS

We studied the worldwide migration of pilgrims traveling to Mecca to perform the Hajj in 2008 using data from the Saudi Ministry of Health and international air traffic departing Saudi Arabia after the 2008 Hajj using worldwide airline ticket sales data. We used gross national income (GNI) per capita as a surrogate marker of a country's ability to mobilize an effective response to H1N1.

RESULTS

In 2008, 2.5 million pilgrims from 140 countries performed the Hajj. Pilgrims (1.7 million) were of international (non-Saudi) origin, of which 91.0% traveled to Saudi Arabia via commercial flights. International pilgrims (11.3%) originated from low-income countries, with the greatest numbers traveling from Bangladesh (50,419), Afghanistan (32,621), and Yemen (28,018).

CONCLUSIONS

Nearly 200,000 pilgrims that performed the Hajj in 2008 originated from the world's most resource-limited countries, where access to H1N1 vaccine and capacity to detect and respond to H1N1 in returning pilgrims are extremely limited. International efforts may be needed to assist resource-limited countries that are vulnerable to the impact of H1N1 during the 2009 to 2010 influenza season.

Emergence and disappearance of W135 meningococcal disease

W135 meningococcal disease was imported into Singapore in 2000 via Hajj pilgrims. Previous studies have showed sustained carriage of W135 with the potential for further transmission within communities. We therefore set out to determine whether W135 meningococcal disease would become endemic in Singapore after its introduction in 2000. Cases occurred until 2003, but no further cases have been reported since 2004.

Global epidemiology of meningococcal disease

As reviewed in this paper, meningococcal disease epidemiology varies substantially by geographic area and time. The disease can occur as sporadic cases, outbreaks, and large epidemics. Surveillance is crucial for understanding meningococcal disease epidemiology, as well as the need for and impact of vaccination. Despite limited data from some regions of the world and constant change, current meningococcal disease epidemiology can be summarized by region. By far the highest incidence of meningococcal disease occurs in the meningitis belt of sub-Saharan Africa. During epidemics, the incidence can approach 1000 per 100,000, or 1% of the population. Serogroup A has been the most important serogroup in this region. However, serogroup C disease has also occurred, as has serogroup X disease and, most recently, serogroup W-135 disease. In the Americas, the reported incidence of disease, in the range of 0.3-4 cases per 100,000 population, is much lower than in the meningitis belt. In addition, in some countries such as the United States, the incidence is at an historical low. The bulk of the disease in the Americas is caused by serogroups C and B, although serogroup Y causes a substantial proportion of infections in some countries and W-135 is becoming increasingly problematic as well. The majority of meningococcal disease in European countries, which ranges in incidence from 0.2 to 14 cases per 100,000, is caused by serogroup B strains, particularly in countries that have introduced serogroup C meningococcal conjugate vaccines. Serogroup B also predominates in Australia and New Zealand, in Australia because of the control of serogroup C disease through vaccination and in New Zealand because of a serogroup B epidemic. Based on limited data, most disease in Asia is caused by serogroup A and C strains. Although this review summarizes the current status of meningococcal disease epidemiology, the dynamic nature of this disease requires ongoing surveillance both to provide data for vaccine formulation and vaccine policy and to monitor the impact of vaccines following introduction.

Polymerase chain reaction for diagnosis and serogrouping of meningococcal disease in children

A prospective study was performed including all children younger than 18 years with the clinical diagnosis of invasive meningococcal disease (IMD) hospitalized at the University Hospital Sant Joan de Déu in Barcelona, Spain, from January 2001 to December 2006. During the study period, 168 meningococcal disease cases were reported. Microbiologic confirmation was obtained in 118 cases. Forty-six (38.9%) of 118 cases were only detected by polymerase chain reaction (PCR); 6 patients were culture positive and PCR negative (5%). Serogroup B predominated in the 6-year period with 83.1% of the strains. A significant decrease in serogroup C was observed in the last 3 years of the study (P=0.029), and less common serogroups, such as serogroup A and W135, emerged. Serogroup distribution of patient diagnoses only by real-time PCR showed a similar distribution: serogroup B, 85.7%; serogroup C, 7.1%; and nontypeable serogroups, 7.1%. In conclusion, real-time PCR is more rapid and sensitive than culture for diagnosis and serogrouping of IMD.

Meningococcal vaccine in travelers

PURPOSE OF REVIEW

New vaccines to prevent meningococcal disease have been licensed in recent years. It is therefore timely to discuss current vaccine strategies pertinent to international travelers in relation to the changing epidemiology.

RECENT FINDINGS

Serogroup W135 achieved epidemic status in Africa in 2002, and then largely disappeared over a short time period. The year 2006 saw a marked epidemic rise in meningitis attack rates across the meningitis belt in Africa. This rise was mainly due to a new serogroup A strain, indicating that a new meningitis epidemic wave is beginning in Africa. Epidemics are also spreading south of the meningitis belt, including the Greater Lakes Area (Burundi, Rwanda, Republic of Tanzania). The new quadrivalent conjugate meningococcal vaccine is now licensed in North America but not elsewhere. In most other industrialized countries, the serogroup C conjugate vaccine is licensed. Plain polysaccharide quadrivalent vaccines are available almost worldwide.

SUMMARY

Quadrivalent meningococcal vaccination is a visa requirement for Hajj and Umrah pilgrims to Saudi Arabia. Travelers to the meningitis belt during the dry season should be advised to receive meningococcal vaccine that covers all four serogroups. This recommendation should be extended to the Greater Lake Area, because of recent epidemics. Vaccine choices depend on availability.

Interactions between Neisseria meningitidis and the complement system

Meningococcal infection remains a worldwide health problem, and understanding the mechanisms by which Neisseria meningitidis evades host innate and acquired immunity is crucial. The complement system is vital for protecting individuals against N. meningitidis. However, this pathogen has evolved several mechanisms to avoid killing by human complement. Bacterial structures such as polysaccharide capsule and those which mimic or bind host molecules function to prevent complement-mediated lysis and phagocytosis. This review provides an update on the recent findings on the diverse mechanisms by which N. meningitidis avoids complement-mediated killing, and how polymorphisms in genes encoding human complement proteins affect susceptibility to this important human pathogen.

Clinical features and outcome of sporadic serogroup W135 disease Taiwan

Background

Few published reports have evaluated the clinical features and outcome of serogroup W135 meningococcal disease. In Taiwan, W135 is the second most prevalent meningococcal disease serogroup.

Method

A nationwide study was conducted to retrospectively analyze epidemiologic data from 115 patients with laboratory confirmed meningococcal disease that occurred from 2001 through 2003.

Results

Serogroup W135 accounted for 26% of all cases and most (76.7%) were older than 20 years. There were no cases of serogroup W135 meningococcal disease associated with Hajj pilgrims, and all cases were sporadic. In 88 patients with complete case records, we compared the presenting symptoms, signs, laboratory data, and outcomes between W135 and non-W135 patients. There were no differences in presenting symptoms except for the higher prevalence of pneumonia found in W135 patients (23.8% vs. 1.5%; OR: 20.6; 95%CI: 2.3–189.0; p = 0.003). The distribution of inflammatory cells in CSF in patients with meningitis was also different between W135 and non-W135 patients. W135 patients had a trend toward more intubations and shock but it did not achieve statistical significance. In multivariate analysis of factors associated with death, three independent factors were found: bacteremia without meningitis, altered mental status, and petechiae or purpura on admission.

Conclusion

Sporadic serogroup W135 meningococcal disease is an important component of the meningococcal disease burden in Taiwan, but it is not directly associated with Hajj pilgrims. Compared with patients infected by other serogroups of meningococci, patients with serogroup W135 were older and more likely to have extrameningeal involvement such as pneumonia.

Meningococcal disease in international travel: vaccine strategies

International travel and migration facilitate the rapid intercontinental spread of meningococcal disease. Serogroup A, and to a lesser extent serogroup C, have been responsible for pandemics in the past (mainly in Africa), but in recent years there was an international outbreak due to W135 related to the Hajj pilgrimage. The high carriage rates, persistence and transmissibility, in combination with the high case fatality rate of the Hajj-associated W135 outbreak clone, certainly raise considerable concern about the public health consequences of widespread dissemination of this organism and the potential for future epidemics. Indeed, the now evolving W135 epidemic in Africa mandates that the bivalent meningococcal vaccine should be replaced by the tetravalent meningococcal vaccine, covering A, C, Y and W135 serogroups. The currently available polysaccharide tetravalent meningococcal vaccine, albeit associated with high seroconversion and efficacy rates, has several shortcomings: it is not immunogenic in young children, duration of protective immunity is short, and it has minimal or no effect on nasopharyngeal carriage and therefore transmission of the organism. Immunogenicity of polysaccharide vaccines can be improved by chemical conjugation to a protein carrier, thereby eliciting a T-cell-dependent antibody response. In contrast to polysaccharide vaccines, conjugate vaccines are immunogenic in young infants, induce long-term protection, and reduce nasopharyngeal carriage. The tetravalent conjugate vaccine will be a leap forward in the control of meningococcal epidemics in affected countries. It will also boost the uptake of meningococcal vaccines in travelers, because the duration of protection is longer and it eliminates the problem of immune hyporesponsiveness of serogroup C with repeated dosing. The small risk of travel-associated disease for the general traveler and the unpredictable nature of epidemics make it difficult to provide evidence-based vaccine recommendations. The current recommendation is to vaccinate all Hajj pilgrims, travelers to areas with current outbreaks, travelers to the sub-Saharan meningitis belt, and high-risk individuals (i.e., those with immunodeficiencies).

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.

Neisseria meningitidis W135, Turkey

We describe the first case of Neisseria meningitidis W135 meningitis in Turkey. The strain was genotypically unrelated to the clone (W)ET-37, isolated from Hajj pilgrims in 2000.

Meningococcal immunology

There is a major need for an effective vaccine against serogroup B disease. The long-term efficacy of the serogroups A, C, Y and W135 conjugate vaccines and the need for booster vaccines has to be determined, as does the effect of changing epidemiology in the United States and worldwide. Control of serogroup A disease in sub-Saharan Africa is a major challenge.

Absence of Neisseria meningitidis W-135 electrophoretic Type 37 during the Hajj, 2002

We document the absence of carriage of Neisseria meningitidis W-135 of the sequence type 11 in returning pilgrims after the Hajj 2002. This finding contrasts with the 15% carriage rate we previously reported in pilgrims returning from the Hajj 2001. The epidemiology of carriage may be changing or may have been controlled by vaccination and a policy of administering antibiotics to pilgrims from countries with a high incidence of meningococcal disease.

Persistence of W135 Neisseria meningitidis carriage in returning Hajj pilgrims: risk for early and late transmission to household contacts

After an outbreak of meningococcal disease caused by Neisseria meningitidis W135, associated with the Hajj pilgrimage in 2001, 15% of returning vaccinated pilgrims carried a single W135 clone, and 55% were still carriers 6 months later. Transmission to 8% of their unvaccinated household contacts occurred within the first few weeks, but no late transmission took place. Public health interventions are needed to protect household contacts.