CURRENT TRENDS IN VACCINES AND VACCINOLOGY

ISSN 2631-8970

The Challenge of Eradicating Meningococcus Outbreaks Through Vaccines

Elijah Ige Ohimain*

Department of Biological Sciences, Niger Delta University, Medical and Public Health Microbiology Research Unit, Wilberforce Island, Bayelsa State, Nigeria

CitationCitation COPIED

Ohimain EI. The Challenge of Eradicating Meningococcus Outbreaks Through Vaccines. Curr Trends Vaccine Vaccinol. 2018 Sep;1(1):105.

Abstract

About 1.0-1.2 million cases of cerebrospinal meningitis infections are recorded each year, with a case fatality of about 70-90% without the use of antibiotics and 10% even with the use of antibiotics. Neisseria meningitidis (Meningococcus) is the major cause of bacterial meningitis all over the world. Due to the combined problem of antibiotics resistance and the development of long-term sequelae/ complications, the use of vaccines could provide the best option for the control of bacterial meningitis. This study reviewed the vaccine strategy for the control of meningococcus and found that three vaccine strategies have been commercialized. The strategy involved vaccine production using capsular polysaccharide, capsular polysaccharide-protein conjugate and outer membrane vesicles. The study also identified challenges of using vaccine to eradicate meningococcus. These problems include the presence of diverse serogroups, strains and clonal complexes of the bacteria inhabiting different geographic locations, lack of cross protection among different vaccines for the different serogroups and high costs of vaccination. More research is therefore required to develop a common vaccine that will protect against all serogroups, strains and clonal complexes of Neisseria meningitidis and possibly the other two species causing bacterial meningitis i.e. Haemophilus influenzaetype b and Streptococcus pneumoniae. Polyvalent vaccine produced using both capsular-protein conjugate and outer membrane vesicle is likely going to be the ideal candidate.

Keywords

Antibiotics; Conjugate Vaccines; Herd Immunity; Meningitis; Outer Membrane Vesicles Vaccine; Polysaccharide Vaccines

Introduction

Since the discovery in 1805 of Neisseria meningitidis (Nm) as the causative agent of meningococcal meningitis, the bacteria have spread globally with different serogroups predominating in different parts of the World. An estimated 1.0- 1.2 million cases are recorded each year [1,2] killing 50-70% of infected person if no treatment is administered [2]. The mortality rate could be reduced to 10% with the administration of antibiotics. Also, neurological complications often occur in over 10% of survivors, such as deafness, brain damage, paralysis, limb loss, learning disabilities [3, 4-7]. Even with adequate antibiotics treatment, about 10% of patients die within 48 hours of the onset of symptoms [6]. Holst et al. [8] reported that prior to the use of antibiotics, the fatality rate of the disease was 70-90%, but dropped to 5-15% with the use of antibiotics, with about 10-15% of survivors developing permanent disabilities. In non-epidemic setting, 10% of healthy individuals carry meningococcus perhaps as normal flora in their upper respiratory tract [7]. Many people may carry the disease in this way, because since 1960, three pandemics of meningitis caused by NmA have occurred in Asia [4]. Neisseria meningitidis A causes seasonal outbreaks of Cerebrospinal Meningitis (CSM) in African meningitis belt.

The attack rate varies with geographical area, being 0.1/100,000 in Mexico and Japan, <1/100,000 persons in USA, >2/100,000 persons in Chile, Brazil and Europe, 5/100,000 in the UK [9] and 20-1000/ 100,000 persons in the extended African meningitis Belt (AMB). The region comprising of 26 countries (Benin, Burkina Faso, Burundi, Cameroun, CAR, Chad, Cote d’Ivorie, DRC, Eritrea, Ethiopia, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Mali, Mauritania, Niger, Nigeria, Rwanda, Senegal, Sudan, South Sudan, Tanzania, Togo and Uganda) with about 450 million people at risk where endemic, epidemic and pandemic outbreaks of meningococcus occur frequently. Endemic rates in Africa is quite high circa 20/100,000, which could increase to 1000/100,000 persons during epidemics [4]. WHO defined epidemic as >100/100,000 population/year. Meningococcal infections often result in meningitis and less commonly meningococcal septicemia also known as meningosepticemia. The symptoms of meningococcal meningitis include headache, fever, photophobia, stiff neck, vomiting and lethargy, while septicemia symptoms include rash, fever, headache, vomiting and abdominal pains [6,7].

Cerebrospinal Meningitis (CSM) is caused mostly by microbial infections, but non-infectious CSM occur rarely due to cancer or the use of drugs that affects the meninges. Different types of microbes have been linked to CSM including bacteria, fungi, yeast, parasites and viruses. Among bacteria, three species have been commonly reported to cause CSM, Neisseria meningitidis, Streptococcus pneumonia and Haemophilus influenza. Recently the WHO ranked H. influenzae (ampicillin resistant) and S. pneumoniae (Penicillin susceptible) as medium priority pathogens requiring the development of new antibiotics [10]. Neisseria meningitidis account for over 80% cases of bacterial meningitis, hence the focus on this organism. Before the use of antibiotics, the fatality of bacterial meningitis was 70-90%, which have reduced to 5-15%, with about 10-20% of survivors developing complications [8], such as hearing impairment, brain damage, and paralysis. Antibiotics resistance has been reported in Neisseria meningitidis. Rouphael and Stephens [9] cited cases of resistance of Nm to sulfonamides, penicillin and Ciprofloxacin. Resistance to Chloramphenicol has also been reported. However, ceftriaxone is currently being used for treatment in the current outbreak of NmC in Nigeria. Due to the combined problem of antibiotics resistance and the development of long-term sequelae/complications, the use of vaccines could provide the best options for the control of bacterial meningitis. Hence, this paper is aimed at presenting updates on meningococcal vaccines and the challenge of using vaccine for the control of meningococcal meningitis.