Emergence and disappearance of W135 meningococcal disease

A mathematical interpretation for outbreaks of bacterial meningitis under the effect of time-dependent transmission parameters

We consider a SIR-type compartmental model divided into two age classes to explain the seasonal exacerbations of bacterial meningitis, especially among children outside of the meningitis belt. We describe the seasonal forcing through time-dependent transmission parameters that may represent the outbreak of the meningitis cases after the annual pilgrimage period (Hajj) or uncontrolled inflows of irregular immigrants. We present and analyse a mathematical model with time-dependent transmission. We consider not only periodic functions in the analysis but also general non-periodic transmission processes. We show that the long-time average values of transmission functions can be used as a stability marker of the equilibrium. Furthermore, we interpret the basic reproduction number in case of time-dependent transmission functions. Numerical simulations support and help visualize the theoretical results.

Meningococcal and pneumococcal carriage in Hajj pilgrims: findings of a randomized controlled trial

BACKGROUND

Intense congestion during the Hajj pilgrimage amplifies the risk of meningococcal carriage and disease, and there have been many meningococcal outbreaks reported amongst pilgrims. Thus, a strict vaccination policy is enforced by the host country and either polysaccharide or conjugate quadrivalent meningococcal vaccines are mandatory. However, unlike conjugate vaccines, the polysaccharide vaccine is not thought to reduce pharyngeal carriage of meningococci.

METHODS

A single-blinded, randomized, controlled trial amongst pilgrims from Saudi Arabia and Australia during the Hajj seasons of 2016-2017 was conducted to compare MenACWY-Conjugate vaccine with MenACWY-Polysaccharide vaccine, to determine if the conjugate vaccine is more effective in reducing asymptomatic carriage of meningococci, and whether the effect may be long-standing. Oropharyngeal swabs were obtained pre-, immediately post- and 6-11 months following completion of Hajj and tested for the presence of meningococci.

RESULTS

Amongst 2000 individuals approached, only 1146 participants aged 18-91 (mean 37.6) years agreed to participate and were randomized to receive either the polysaccharide (n = 561) or the conjugate (n = 561) vaccine, 60.8% were male, and 93.5% were from Saudi Arabia. Amongst oropharyngeal swabs obtained before Hajj, only two (0.2%) tested positive for Neisseria meningitidis. Similarly, meningococci were identified in only one sample at each of the post-Hajj and late follow-up visits. None of the carriage isolates were amongst the serogroups covered by the vaccines. A post hoc analysis of the third swabs revealed that 22.4% of all participants (50/223) were positive for Streptococcus pneumoniae nucleic acid.

CONCLUSION

The low overall carriage rate of meningococci found amongst Hajj pilgrims in 2016 and 2017 demonstrates a successful vaccination policy, but neither supports nor refutes the superiority of meningococcal conjugate ACWY vaccine over the polysaccharide vaccine against carriage. Although an association could not be established in this study, molecular epidemiology would help to establish the role of Hajj in facilitating transmission of pneumococci and inform vaccination policy.

Atypical presentation of invasive meningococcal disease caused by serogroup W meningococci

Neisseria meningitidis, a gram-negative diplococcus, is typically an asymptomatic coloniser of the oropharynx and nasopharynx. Passage of N. meningitidis into the bloodstream can cause invasive meningococcal disease (IMD), a potentially life-threatening illness with rapid onset that generally presents as meningitis, septicemia or both. Serogroup W IMD has been increasing in prevalence in recent years, and observations suggest that it may present with atypical signs and symptoms. Herein, a literature search was performed to identify trends in atypical serogroup W IMD presentation in order to review those that are most prevalent. Findings indicate that the most prevalent atypical presentations of serogroup W IMD include acute gastrointestinal (GI) symptoms, septic arthritis and bacteremic pneumonia or severe upper respiratory tract infection, notably epiglottitis. Atypical clinical presentation is associated with higher case fatality rates and can lead to misdiagnoses. Such risks highlight the need for clinicians to consider IMD in their differential diagnoses of patients with acute GI symptoms, septic arthritis or bacteremic pneumonia, primarily in regions where serogroup W is prevalent.

Global epidemiology of capsular group W meningococcal disease (1970-2015): Multifocal emergence and persistence of hypervirulent sequence type (ST)-11 clonal complex

Following an outbreak in Mecca Saudi Arabia in 2000, meningococcal strains expressing capsular group W (W) emerged as a major cause of invasive meningococcal disease (IMD) worldwide. The Saudi Arabian outbreak strain (Hajj clone) belonging to the ST-11 clonal complex (cc11) is similar to W cc11 causing occasional sporadic disease before 2000. Since 2000, W cc11 has caused large meningococcal disease epidemics in the African meningitis belt and endemic disease in South America, Europe and China. Traditional molecular epidemiologic typing suggested that a majority of current W cc11 burden represented global spread of the Hajj clone. However, recent whole genome sequencing (WGS) analyses revealed significant genetic heterogeneity among global W cc11 strains. While continued spread of the Hajj clone occurs in the Middle East, the meningitis belt and South Africa have co-circulation of the Hajj clone and other unrelated W cc11 strains. Notably, South America, the UK, and France share a genetically distinct W cc11 strain. Other W lineages persist in low numbers in Europe, North America and the meningitis belt. In summary, WGS is helping to unravel the complex genomic epidemiology of group W meningococcal strains. Wider application of WGS and strengthening of global IMD surveillance is necessary to monitor the continued evolution of group W lineages.

Review of invasive meningococcal disease during the last 40 years in Turkey

Due to the lack of comprehensive surveillance data representing Turkey, the authors aimed to derive information by panoramically reviewing all articles related to invasive meningococcal disease (IMD) published in the last 40 years. The following databases were reviewed: Ulakbim (the national database), BIOSIS Previews (from 1995), Evidence-Based Medicine Reviews-Cochrane Database of Systematic Reviews (from 2005), Embase (from 1996), Ovid MEDLINE(R) (from 1946) and Journals@Ovid Full Text (2014). Twenty-seven articles, 10 published in international journals and 17 in national journals, were identified. Only two were multicenter sentinel meningitis surveillance studies. Also, 74% of IMD patients were aged 5 years or younger and the median overall case fatality rate during childhood was 18.44%. Turkey is a country where meningococcal vaccination on a national basis is recommended by WHO. A vaccination strategy for serogroups B and W135 targeting the first 5 years, covering especially the first 12 months, would be appropriate.

Cluster of serogroup W-135 meningococcal disease in 3 military recruits

We describe a group of 3 cases of invasive meningococcal disease that occurred in a military training camp in April 2011. All three patients were hospitalized. Ultimately, two patients recovered and one died. One patient had meningitis, one patient had septicemia and meningitis, and the other had no definite septicemia or meningitis. Neisseria meningitidis serogroup W-135 was detected in the serum and cerebrospinal fluid (CSF) of all patients by real-time polymerase chain reaction. In the one case of mortality, two strains were isolated from the patient's blood and CSF. Using multilocus sequence typing analysis, these strains were identified as a novel sequence type, ST-8912. Special attention is required for the meningococcal disease in military camp because the military personnels are in high risk of contact transmission.

PCR-based national bacterial meningitis surveillance in Turkey: years 2006 to 2009

Polymerase chain reaction-based surveillance for bacterial meningitis including 841 children revealed 246 with bacterial DNA in cerebrospinal fluid samples of which 53% were Streptococcus pneumoniae, 19% Neisseria meningitidis, and 16% Haemophilus influenzae type b. The most common S. pneumoniae serotypes/serogroups were 1, 19F, 6A/6B, 23F, 5, 14, 18 and 19A. Among 47 meningococci, 86% were serogroup B, 6% serogroup C, 3% serogroup A, 3% serogroup X and 3% serogroup W.

Serogroup W meningococcal disease: global spread and current affect on the Southern Cone in Latin America

Meningococcal serogroup W strains have been emerging throughout the current century with most of the isolates belonging to the sequence type (ST11)/electrophoretic type (ET37) clonal complex (ST11/E37 CC), particularly since the international outbreak following Hajj 2000. That outbreak appears to have triggered off that trend, contributing to the spread of W ST11/ET37 CC strains globally; however, local strains could be also responsible for increases in the percentage and/or incidence rates of this serogroup in some countries. More recently, unexpected increases in the percentage and incidence rate of W has been noticed in different countries located in the South Cone in Latin America, and W ST11/ET37 CC strains now appear as endemic in the region and an extensive immunization programme with tetravalent conjugate vaccine (covering serogroups A, C, Y and W) has been recently implemented in Chile. It is difficult to ascertain whether we are observing the emergence of W ST11 CC strains in different geographical areas or whether the Hajj 2000 strain is still spreading globally. Several aspects of the evolution of that situation are analysed in this paper, reviewing also the implications in immunization programmes. Closely related with the analysis of this potential evolution, it will be very interesting to monitor the evolution of serogroup W in the African meningitis belt after implementation of the extensive immunization programme with serogroup A conjugate vaccine that is currently underway. More data about carriers, transmission, clonal lineages, etc. are needed for taking decisions (target groups, outbreak control, defining the extent, etc.) to adapt the response strategy with potential interventions with broad coverage vaccines against the emergent serogroup W.

Meningococcal serogroup B disease in Turkey: a guess or reality?

Each country chooses the appropriate vaccine against IMD depending on the locally prevalent serogroups of N. meningitides. Frequency of each meningococcal serogroup varies considerably over time and by geographical location. Despite the majority of IMD cases (85%) are caused by serogroups B and C in Europe, true prevalence of serogroup B IMD cases in Turkey is unclear. In one of the recent studies, the sharp decrease of serogroup B IMD from 35% down to 2.5% in a few years despite the absence of vaccination is confusing. Millions of European Turkish people travels from Europe to Turkey every year who could most probably carry serogroup B. It is obvious that a nationwide active surveillance is crucial to assess the the true epidemiology and burden of IMD which has a major impact on the choice of vaccine type and age interval the vaccination to be implemented.

Review of meningococcal vaccines with updates on immunization in adults

Meningococcal disease is a serious and global life-threatening disease. Six serogroups (A, B, C, W-135, X, and Y) account for the majority of meningococcal disease worldwide. Meningococcal polysaccharide vaccines were introduced several decades ago and have led to the decline in the burden of disease. However, polysaccharide vaccines have several limitations, including poor immunogenicity in infants and toddlers, short-lived protection, lack of immunologic memory, negligible impact on nasopharyngeal carriage, and presence of hyporesponsiveness after repeated doses. The chemical conjugation of plain polysaccharide vaccines has the potential to overcome these drawbacks. Meningococcal conjugate vaccines include the quadrivalent vaccines (MenACWY-DT, MenACWY-CRM, and MenACWY-TT) as well as the monovalent A and C vaccines. These conjugate vaccines were shown to elicit strong immune response in adults. This review addresses the various aspects of meningococcal disease, the limitations posed by polysaccharide vaccines, the different conjugate vaccines with their immunogenicity and reactogenicity in adults, and the current recommendations in adults.

Considerations for controlling invasive meningococcal disease in high income countries

The development of conjugate vaccines has enabled the prevention and control of Neisseria meningitidis caused by serogroups A, C, W-135 and Y. Vaccines that provide protection against a broad number of serogroup B strains likely will be available soon to enable greater control of meningococcal disease in high income countries. We present an argument for adequate post-marketing surveillance to monitor epidemiological shifts and to provide a context for the safety and reactogenicity of serogroup B vaccines, including the newer recombinant vaccines. We also offer a series of recommendations to address possible concerns about vaccine safety.

The changing and dynamic epidemiology of meningococcal disease

The epidemiology of invasive meningococcal disease continues to change rapidly, even in the three years since the first Meningococcal Exchange Meeting in 2008. Control of disease caused by serogroup C has been achieved in countries that have implemented meningococcal C or quadrivalent meningococcal ACWY conjugate vaccines. Initiation of mass immunization programs with meningococcal A conjugate vaccines across the meningitis belt of Africa may lead to the interruption of cyclical meningococcal epidemics. A meningococcal B vaccination program in New Zealand has led to a decreased incidence of high rates of endemic serogroup B disease. Increases in serogroup Y disease have been observed in certain Nordic countries which, if they persist, may require consideration of use of a multiple serogroup vaccine. The imminent availability of recombinant broadly protective serogroup B vaccines may provide the tools for further control of invasive meningococcal disease in areas where serogroup B disease predominates. Continued surveillance of meningococcal disease is essential; ongoing global efforts to improve the completeness of reporting are required.

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.