The Strengthening of Laboratory Systems in the Meningitis Belt to Improve Meningitis Surveillance, 2008-2018: A Partners' Perspective

Immunologic biomarkers for bacterial meningitis

Meningitis is defined as the inflammation of the meninges that is most often caused by various bacterial and viral pathogens, and is associated with high rates of mortality and morbidity. Early detection of bacterial meningitis is essential to appropriate antibiotic therapy. Alterations in immunologic biomarkers levels have been considered the diagnostic approach in medical laboratories for the identifying of infections. The early increasing immunologic mediators such as cytokines and acute phase proteins (APPs) during bacterial meningitis have made they significant indicators for laboratory diagnosis. Immunology biomarkers showed wide variable sensitivity and specificity values that influenced by different reference values, selected a certain cutoff point, methods of detection, patient characterization and inclusion criteria, as well as etiology of meningitis and time of CSF or blood specimens' collection. This study provides an overview of different immunologic biomarkers as diagnostic markers for the identification of bacterial meningitis and their efficiencies in the differentiating of bacterial from viral meningitis.

Global, regional, and national burden of meningitis and its aetiologies, 1990-2019: a systematic analysis for the Global Burden of Disease Study 2019

BACKGROUND

Although meningitis is largely preventable, it still causes hundreds of thousands of deaths globally each year. WHO set ambitious goals to reduce meningitis cases by 2030, and assessing trends in the global meningitis burden can help track progress and identify gaps in achieving these goals. Using data from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019, we aimed to assess incident cases and deaths due to acute infectious meningitis by aetiology and age from 1990 to 2019, for 204 countries and territories.

METHODS

We modelled meningitis mortality using vital registration, verbal autopsy, sample-based vital registration, and mortality surveillance data. Meningitis morbidity was modelled with a Bayesian compartmental model, using data from the published literature identified by a systematic review, as well as surveillance data, inpatient hospital admissions, health insurance claims, and cause-specific meningitis mortality estimates. For aetiology estimation, data from multiple causes of death, vital registration, hospital discharge, microbial laboratory, and literature studies were analysed by use of a network analysis model to estimate the proportion of meningitis deaths and cases attributable to the following aetiologies: Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae, group B Streptococcus, Escherichia coli, Klebsiella pneumoniae, Listeria monocytogenes, Staphylococcus aureus, viruses, and a residual other pathogen category.

FINDINGS

In 2019, there were an estimated 236 000 deaths (95% uncertainty interval [UI] 204 000-277 000) and 2·51 million (2·11-2·99) incident cases due to meningitis globally. The burden was greatest in children younger than 5 years, with 112 000 deaths (87 400-145 000) and 1·28 million incident cases (0·947-1·71) in 2019. Age-standardised mortality rates decreased from 7·5 (6·6-8·4) per 100 000 population in 1990 to 3·3 (2·8-3·9) per 100 000 population in 2019. The highest proportion of total all-age meningitis deaths in 2019 was attributable to S pneumoniae (18·1% [17·1-19·2]), followed by N meningitidis (13·6% [12·7-14·4]) and K pneumoniae (12·2% [10·2-14·3]). Between 1990 and 2019, H influenzae showed the largest reduction in the number of deaths among children younger than 5 years (76·5% [69·5-81·8]), followed by N meningitidis (72·3% [64·4-78·5]) and viruses (58·2% [47·1-67·3]).

INTERPRETATION

Substantial progress has been made in reducing meningitis mortality over the past three decades. However, more meningitis-related deaths might be prevented by quickly scaling up immunisation and expanding access to health services. Further reduction in the global meningitis burden should be possible through low-cost multivalent vaccines, increased access to accurate and rapid diagnostic assays, enhanced surveillance, and early treatment.

FUNDING

Bill & Melinda Gates Foundation.

Enhancing Meningococcal Genomic Surveillance in the Meningitis Belt Using High-Resolution Culture-Free Whole-Genome Sequencing

Rollout of meningococcal serogroup A conjugate vaccine in Africa started in 2010, aiming to eliminate meningitis outbreaks, in meningitis belt countries. Since then, studies have been conducted, primarily using isolates, to assess the vaccine impact on the distribution of meningococcal strains in the region. Here, we implemented an innovative, culture-free whole-genome sequencing approach on almost 400 clinical specimens collected between 2017 and 2019 from meningococcal meningitis cases in 6 African countries. About 50% of specimens provided high-quality whole-genome sequence data for comprehensive molecular profiling of the meningococcal pathogen. Three major clonal complexes were identified: CC11 associated with serogroup W, CC181 associated with serogroup X, and CC10217 associated with serogroup C, which continues to rise as a predominant clonal complex in the region. Genomic surveillance for meningococcal meningitis can be significantly improved using culture-free methods to increase data representativeness and monitor changes in epidemiological landscape, especially for countries with low culture rate.

Establishing a national reference laboratory for antimicrobial resistance using a whole-genome sequencing framework: Nigeria's experience

Whole-genome sequencing (WGS) is finding important applications in the surveillance of antimicrobial resistance (AMR), providing the most granular data and broadening the scope of niches and locations that can be surveilled. A common but often overlooked application of WGS is to replace or augment reference laboratory services for AMR surveillance. WGS has supplanted traditional strain subtyping in many comprehensive reference laboratories and is now the gold standard for rapidly ruling isolates into or out of suspected outbreak clusters. These and other properties give WGS the potential to serve in AMR reference functioning where a reference laboratory did not hitherto exist. In this perspective, we describe how we have employed a WGS approach, and an academic-public health system collaboration, to provide AMR reference laboratory services in Nigeria, as a model for leapfrogging to national AMR surveillance.

Prevalence, Antibiogram, and Associated Factors of Bacteria Isolated From Presumptive Meningitis Patients at Debre Markos Comprehensive Specialized Hospital, Northwest Ethiopia

OBJECTIVE

Bacterial meningitis (BM) is a public health threat with considerable mortality and morbidity worldwide; particularly in the meningitis belt of Africa where Ethiopia is located. The study aims to assess the prevalence, antibiogram, and associated factors of bacteria isolated from presumptive meningitis patients at Debre Markos Comprehensive Specialized Hospital (DMCSH), Northwest Ethiopia.

METHODS

We conducted a cross-sectional study between March 1, 2021, and May 30, 2021. Socio-demographic and clinical data were collected using structured questionnaires. Cerebrospinal fluid (CSF) was collected aseptically, and gram stain, culture, and biochemical tests were performed to identify bacterial isolates. An antimicrobial susceptibility test was conducted using the disc diffusion method on Mueller-Hinton agar (MHA). Data were entered into EpiData version 3.1 (Epidata Association, Denmark) and exported to SPSS version 23 software (IBM Corp., Armonk, NY) for analysis. P values ≤ 0.05 at 95% CI were considered statistically significant.

RESULTS

CSF samples from 152 study participants were analyzed and half (50%, 76/152) of them were males. Bacteria were isolated from 17 individuals with an overall prevalence rate of 11.2% (95% CI= 5.9-16.4). The predominant bacterial isolates were Staphylococcus aureus (S. aureus) and Klebsiella pneumonia (K. pneumoniae) each accounting for 29.4% (5/17). About 41% (7/17) of the isolated bacteria were found to be multi-drug resistant (MDR) with the predominance of gram-negative bacteria (6/7). Bacteria prevalence was significantly higher in individuals with stiff neck [adjusted odds ratio (AOR), 95% CI, 47.529 (3.2-10.92), P=0.023] and tonsillectomy [AOR, 95% CI, 137.015 (6.25-12.34), P=0.02].

CONCLUSION

S. aureus and K. pneumoniae were the leading isolates among presumptive meningitis patients. The alarming presence of a high rate of MDR isolates mandates the need to implement the antibiotic stewardship program in the study setting.

Neisseria meningitidis Serogroup C Clonal Complex 10217 Outbreak in West Kpendjal Prefecture, Togo 2019

Togo has reported seasonal meningitis outbreaks caused by non-Neisseria meningitidis serogroup A (NmA) pathogens since the introduction of meningococcal serogroup A conjugate vaccine (MACV, MenAfriVac) in 2014. From 2016 to 2017, NmW caused several outbreaks. In early 2019, a NmC outbreak was detected in the Savanes region of Togo and its investigation is described here. Under case-based surveillance, epidemiological and clinical data, and cerebrospinal fluid specimens were collected for every suspected case of meningitis. Specimens were tested for meningitis pathogens using confirmatory microbiological and molecular methods. During epidemic weeks 9 to 15, 199 cases were reported, with 179 specimens being available for testing and 174 specimens (97.2%) were tested by at least one confirmatory method. The NmC was the predominant pathogen confirmed (93.9%), belonging to sequence type (ST)-9367 of clonal complex (CC) 10217. All NmC cases were localized to the West Kpendjal district of the Savanes region with attack rates ranging from 4.1 to 18.8 per 100,000 population and case fatality rates ranging up to 2.2% during weeks 9 to 15. Of the 93 NmC confirmed cases, 63.4% were males and 88.2% were in the 5 to 29 age group. This is the first report of a NmC meningitis outbreak in Togo. The changing epidemiology of bacterial meningitis in the meningitis belt post-MACV highlights the importance of monitoring of emerging strain and country preparedness for outbreaks in the region.

IMPORTANCE The recent emergence of an invasive NmC strain in Togo is an example of the changing bacterial meningitis epidemiology in the meningitis belt post-MACV. The current epidemiology includes the regional circulation of various non-NmA serogroups, which emphasizes the need for effective molecular surveillance, laboratory diagnosis, and a multivalent vaccine that is effective against all serogroups in circulation.

Good Financial Grant Practice: A Tool for Developing and Demonstrating Institutional Financial and Grant Management Capacity in Global Health

The administration and governance of grant funding across global health organizations presents enormous challenges. Meeting these challenges is crucial to ensuring that funds are used in the most effective way to improve health outcomes, in line with the United Nations' Sustainable Development Goal 3, "Ensure healthy lives and promote well-being for all at all ages." The Good Financial Grant Practice (GFGP) Standard (ARS 1651) is the world's first and, currently, only international standard for the financial governance and management of grant funding. Through consensus building and global harmonization between both low- and middle-income and high-income country players, the GFGP Standard has achieved a leveling impact: GFGP applies equally to, and can be implemented by, all types of organization, regardless of location, size, or whether they predominantly give or receive funding. GFGP can be used as a tool for addressing some of the challenges of the current funding model. Here, we describe our experiences and lessons learned from implementing GFGP across 4 diverse research institutions in India, Nigeria, Colombia, and the Philippines as part of our National Institute for Health Research Global Health Research Unit on Genomic Surveillance of Antimicrobial Resistance.

The novel biphasic medium for transport, culture and conservation at an ambient temperature of Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influenzae

Bacterial meningitis remains a very important disease worldwide, and the major causative pathogens were Neisseria meningitidis (N. meningitidis), Streptococcus pneumoniae (S. pneumoniae) and Haemophilus influenzae (H. influenzae). In our context, the technical difficulties encountered in the routine practice were associated with the fragility of these bacteria, the high rates of negative culture and the demanding transport conditions. That's why the need to look for a solution to its technical problems and to propose a new proper solution with the local situation. The aim of this study was to develop, perform and evaluate a novel biphasic medium used for the transport, culture and conservation at an ambient temperature of N. meningitidis, S. pneumoniae and H. influenzae. The results showed that this biphasic medium provided more, novels and easy nutriments through the addition of liquid phase and solid phase medium and it was found to be conducive to the growth and conservation of N. meningitidis, S. pneumoniae and H. influenzae at an ambient temperature of a minimum of 40 days. And the ingredients used in the medium are readily available at a low cost as well as the components prepared in large quantities, they could be stored at + 4 ± 1 °C for 2 years without significantly altering their growth and conservation supporting their potential. The survival and recovery for the fastidious bacteria on the biphasic medium and the other media used for comparison in this study were significantly different (P < 0.05). In addition, the Sensitivity, Specificity, Positive and Negative Predictive Value of biphasic medium showed highest among the three bacteria at least 40 days of storage at room temperature in this study. In conclusion, we found the biphasic medium to be low cost and suitable for previously mentioned bacteria from suspected meningitis patients, offering an optimal condition and an increase in the viability of the isolates at ambient temperature. And it was concluded that this biphasic medium could be used as a technical solution in laboratories for the management of meningitis.

Molecular diagnostic assays for the detection of common bacterial meningitis pathogens: A narrative review

Bacterial meningitis is a major global cause of morbidity and mortality. Rapid identification of the aetiological agent of meningitis is essential for clinical and public health management and disease prevention given the wide range of pathogens that cause the clinical syndrome and the availability of vaccines that protect against some, but not all, of these. Since microbiological culture is complex, slow, and often impacted by prior antimicrobial treatment of the patient, molecular diagnostic assays have been developed for bacterial detection. Distinguishing between meningitis caused by Neisseria meningitidis (meningococcus), Streptococcus pneumoniae (pneumococcus), Haemophilus influenzae, and Streptococcus agalactiae and identifying their polysaccharide capsules is especially important. Here, we review methods used in the identification of these bacteria, providing an up-to-date account of available assays, allowing clinicians and diagnostic laboratories to make informed decisions about which assays to use.

Full Molecular Typing of Neisseria meningitidis Directly from Clinical Specimens for Outbreak Investigation

Neisseria meningitidis is a leading cause of bacterial meningitis and sepsis worldwide and an occasional cause of meningococcal urethritis. When isolates are unavailable for surveillance or outbreak investigations, molecular characterization of pathogens needs to be performed directly from clinical specimens, such as cerebrospinal fluid (CSF), blood, or urine. However, genome sequencing of specimens is challenging because of low bacterial and high human DNA abundances. We developed selective whole-genome amplification (SWGA), an isothermal multiple-displacement amplification-based method, to efficiently enrich, sequence, and de novo assemble N. meningitidis DNA from clinical specimens with low bacterial loads. SWGA was validated with 12 CSF specimens from invasive meningococcal disease cases and 12 urine specimens from meningococcal urethritis cases. SWGA increased the mean proportion of N. meningitidis reads by 2 to 3 orders of magnitude, enabling identification of at least 90% of the 1,605 N. meningitidis core genome loci for 50% of the specimens. The validated method was used to investigate two meningitis outbreaks recently reported in Togo and Burkina Faso. Twenty-seven specimens with low bacterial loads were processed by SWGA before sequencing, and 12 of 27 were successfully assembled to obtain the full molecular typing and vaccine antigen profile of the N. meningitidis pathogen, thus enabling thorough characterization of outbreaks. This method is particularly important for enhancing molecular surveillance in regions with low culture rates. SWGA produces enough reads for phylogenetic and allelic analysis at a low cost. More importantly, the procedure can be extended to enrich other important human bacterial pathogens.

MenAfriNet: A Network Supporting Case-Based Meningitis Surveillance and Vaccine Evaluation in the Meningitis Belt of Africa

Meningococcal meningitis remains a significant public health threat, especially in the African meningitis belt where Neisseria meningitidis serogroup A historically caused large-scale epidemics. With the rollout of a novel meningococcal serogroup A conjugate vaccine (MACV) in the belt, the World Health Organization recommended case-based meningitis surveillance to monitor MACV impact and meningitis epidemiology. In 2014, the MenAfriNet consortium was established to support strategic implementation of case-based meningitis surveillance in 5 key countries: Burkina Faso, Chad, Mali, Niger, and Togo. MenAfriNet aimed to develop a high-quality surveillance network using standardized laboratory and data collection protocols, develop sustainable systems for data management and analysis to monitor MACV impact, and leverage the surveillance platform to perform special studies. We describe the MenAfriNet consortium, its history, strategy, implementation, accomplishments, and challenges.

Meningococcal Meningitis Outbreaks in the African Meningitis Belt After Meningococcal Serogroup A Conjugate Vaccine Introduction, 2011-2017

BACKGROUND

In 2010-2017, meningococcal serogroup A conjugate vaccine (MACV) was introduced in 21 African meningitis belt countries. Neisseria meningitidis A epidemics have been eliminated here; however, non-A serogroup epidemics continue.

METHODS

We reviewed epidemiological and laboratory World Health Organization data after MACV introduction in 20 countries. Information from the International Coordinating Group documented reactive vaccination.

RESULTS

In 2011-2017, 17 outbreaks were reported (31 786 suspected cases from 8 countries, 1-6 outbreaks/year). Outbreaks were of 18-14 542 cases in 113 districts (median 3 districts/outbreak). The most affected countries were Nigeria (17 375 cases) and Niger (9343 cases). Cumulative average attack rates per outbreak were 37-203 cases/100 000 population (median 112). Serogroup C accounted for 11 outbreaks and W for 6. The median proportion of laboratory confirmed cases was 20%. Reactive vaccination was conducted during 14 outbreaks (5.7 million people vaccinated, median response time 36 days).

CONCLUSION

Outbreaks due to non-A serogroup meningococci continue to be a significant burden in this region. Until an affordable multivalent conjugate vaccine becomes available, the need for timely reactive vaccination and an emergency vaccine stockpile remains high. Countries must continue to strengthen detection, confirmation, and timeliness of outbreak control measures.

Implementation of Case-Based Surveillance and Real-time Polymerase Chain Reaction to Monitor Bacterial Meningitis Pathogens in Chad

BACKGROUND

Meningococcal serogroup A conjugate vaccine (MACV) was introduced in Chad during 2011-2012. Meningitis surveillance has been conducted nationwide since 2003, with case-based surveillance (CBS) in select districts from 2012. In 2016, the MenAfriNet consortium supported Chad to implement CBS in 4 additional districts and real-time polymerase chain reaction (rt-PCR) at the national reference laboratory (NRL) to improve pathogen detection. We describe analysis of bacterial meningitis cases during 3 periods: pre-MACV (2010-2012), pre-MenAfriNet (2013-2015), and post-MenAfriNet (2016-2018).

METHODS

National surveillance targeted meningitis cases caused by Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae. Cerebrospinal fluid specimens, inoculated trans-isolate media, and/or isolates from suspected meningitis cases were tested via culture, latex, and/or rt-PCR; confirmed bacterial meningitis was defined by a positive result on any test. We calculated proportion of suspected cases with a specimen received by period, and proportion of specimens with a bacterial meningitis pathogen identified, by period, pathogen, and test.

RESULTS

The NRL received specimens for 6.8% (876/12813), 46.4% (316/681), and 79.1% (787/995) of suspected meningitis cases in 2010-2012, 2013-2015, and 2016-2018, respectively, with a bacterial meningitis pathogen detected in 33.6% (294/876), 27.8% (88/316), and 33.2% (261/787) of tested specimens. The number of N. meningitidis serogroup A (NmA) among confirmed bacterial meningitis cases decreased from 254 (86.4%) during 2010-2012 to 2 (2.3%) during 2013-2015, with zero NmA cases detected after 2014. In contrast, proportional and absolute increases were seen between 2010-2012, 2013-2015, and 2016-2018 in cases caused by S. pneumoniae (5.1% [15/294], 65.9% [58/88], and 52.1% [136/261]), NmX (0.7% [2/294], 1.1% [1/88], and 22.2% [58/261]), and Hib (0.3% [1/294], 11.4% [10/88], and 14.9% [39/261]). Of specimens received at the NRL, proportions tested during the 3 periods were 47.7% (418), 53.2% (168), and 9.0% (71) by latex; 81.4% (713), 98.4% (311), and 93.9% (739) by culture; and 0.0% (0), 0.0% (0), and 90.5% (712) by rt-PCR, respectively. During the post-MenAfriNet period (2016-2018), 86.1% (678) of confirmed cases were tested by both culture and rt-PCR, with 12.5% (85) and 32.4% (220) positive by culture and rt-PCR, respectively.

CONCLUSIONS

CBS implementation was associated with increased specimen referral. Increased detection of non-NmA cases could reflect changes in incidence or increased sensitivity of case detection with rt-PCR. Continued surveillance with the use of rt-PCR to monitor changing epidemiology could inform the development of effective vaccination strategies.

Future Directions for Meningitis Surveillance and Vaccine Evaluation in the Meningitis Belt of Sub-Saharan Africa

In sub-Saharan Africa, bacterial meningitis remains a significant public health problem, especially in the countries of the meningitis belt, where Neisseria meningitidis serogroup A historically caused large-scale epidemics. In 2014, MenAfriNet was established as a consortium of partners supporting strategic implementation of case-based meningitis surveillance to monitor meningitis epidemiology and impact of meningococcal serogroup A conjugate vaccine (MACV). MenAfriNet improved data quality through use of standardized tools, procedures, and laboratory diagnostics. MenAfriNet surveillance and study data provided evidence of ongoing MACV impact, characterized the burden of non-serogroup A meningococcal disease (including the emergence of a new epidemic clone of serogroup C), and documented the impact of pneumococcal conjugate vaccine. New vaccines and schedules have been proposed for future implementation to address the remaining burden of meningitis. To support the goals of "Defeating Meningitis by 2030," MenAfriNet will continue to strengthen surveillance and support research and modeling to monitor the impact of these programs on meningitis burden in sub-Saharan Africa.

Epidemiology of Bacterial Meningitis in the Nine Years Since Meningococcal Serogroup A Conjugate Vaccine Introduction, Niger, 2010-2018

BACKGROUND

In 2010, Niger and other meningitis belt countries introduced a meningococcal serogroup A conjugate vaccine (MACV). We describe the epidemiology of bacterial meningitis in Niger from 2010 to 2018.

METHODS

Suspected and confirmed meningitis cases from January 1, 2010 to July 15, 2018 were obtained from national aggregate and laboratory surveillance. Cerebrospinal fluid specimens were analyzed by culture and/or polymerase chain reaction. Annual incidence was calculated as cases per 100 000 population. Selected isolates obtained during 2016-2017 were characterized by whole-genome sequencing.

RESULTS

Of the 21 142 suspected cases of meningitis, 5590 were confirmed: Neisseria meningitidis ([Nm] 85%), Streptococcus pneumoniae ([Sp] 13%), and Haemophilus influenzae ([Hi] 2%). No NmA cases occurred after 2011. Annual incidence per 100 000 population was more dynamic for Nm (0.06-7.71) than for Sp (0.18-0.70) and Hi (0.01-0.23). The predominant Nm serogroups varied over time (NmW in 2010-2011, NmC in 2015-2018, and both NmC and NmX in 2017-2018). Meningococcal meningitis incidence was highest in the regions of Niamey, Tillabery, Dosso, Tahoua, and Maradi. The NmW isolates were clonal complex (CC)11, NmX were CC181, and NmC were CC10217.

CONCLUSIONS

After MACV introduction, we observed an absence of NmA, the emergence and continuing burden of NmC, and an increase in NmX. Niger's dynamic Nm serogroup distribution highlights the need for strong surveillance programs to inform vaccine policy.

Bacterial Meningitis Epidemiology in Five Countries in the Meningitis Belt of Sub-Saharan Africa, 2015-2017

BACKGROUND

The MenAfriNet Consortium supports strategic implementation of case-based meningitis surveillance in key high-risk countries of the African meningitis belt: Burkina Faso, Chad, Mali, Niger, and Togo. We describe bacterial meningitis epidemiology in these 5 countries in 2015-2017.

METHODS

Case-based meningitis surveillance collects case-level demographic and clinical information and cerebrospinal fluid (CSF) laboratory results. Neisseria meningitidis, Streptococcus pneumoniae, or Haemophilus influenzae cases were confirmed and N. meningitidis/H. influenzae were serogrouped/serotyped by real-time polymerase chain reaction, culture, or latex agglutination. We calculated annual incidence in participating districts in each country in cases/100 000 population.

RESULTS

From 2015-2017, 18 262 suspected meningitis cases were reported; 92% had a CSF specimen available, of which 26% were confirmed as N. meningitidis (n = 2433; 56%), S. pneumoniae (n = 1758; 40%), or H. influenzae (n = 180; 4%). Average annual incidences for N. meningitidis, S. pneumoniae, and H. influenzae, respectively, were 7.5, 2.5, and 0.3. N. meningitidis incidence was 1.5 in Burkina Faso, 2.7 in Chad, 0.4 in Mali, 14.7 in Niger, and 12.5 in Togo. Several outbreaks occurred: NmC in Niger in 2015-2017, NmC in Mali in 2016, and NmW in Togo in 2016-2017. Of N. meningitidis cases, 53% were NmC, 30% NmW, and 13% NmX. Five NmA cases were reported (Burkina Faso, 2015). NmX increased from 0.6% of N. meningitidis cases in 2015 to 27% in 2017.

CONCLUSIONS

Although bacterial meningitis epidemiology varied widely by country, NmC and NmW caused several outbreaks, NmX increased although was not associated with outbreaks, and overall NmA incidence remained low. An effective low-cost multivalent meningococcal conjugate vaccine could help further control meningococcal meningitis in the region.