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Five things you need to know about the world’s latest weapon against bacterial meningitis

The Men5CV (MenFive) pentavalent meningitis vaccine could help eliminate a leading cause of neurological disease and disability in sub-Saharan Africa.

Meningococcal disease is a major cause of hearing loss, brain damage and limb amputations, and despite the introduction of a highly effective vaccine, remains the second biggest infectious killer of young children worldwide. A key reason is that it is not just caused by one type of bacterium, but many. Now the world stands on the brink of a historic milestone: the roll-out of a vaccine that protects against the five leading causes of this deadly and debilitating disease.

Children with their vaccination cards during a vaccination campaign against meningitis A in Chad. Credit: Gavi/2018

Here are five things you should know about it:

1. Vaccination is a highly effective strategy against meningococcal disease.

Meningitis is a serious infection of the thin membrane surrounding the brain and spinal cord that can cause severe brain damage and is fatal in up to 80% of cases if untreated. Several different bacteria can cause it, but Neisseria meningitidis (meningococcus) is responsible for causing large and deadly epidemics in the region of sub-Saharan Africa known as the African meningitis belt, which has the highest rates of meningococcal disease in the world.

The MenFive vaccine is expected to be more accessible to meningitis belt countries than existing meningococcal conjugate vaccines that protect against multiple serogroups

Historically, major epidemics have swept through these countries every five to 12 years. But the introduction of the MenAfriVac vaccine since 2010 has resulted in the virtual elimination of the leading cause of epidemic meningitis – Group A meningococcus – saving millions of lives.

Part of what has made it so effective is that, unlike earlier meningococcus vaccines, the MenAfriVac vaccine links – or "conjugates" – complex sugars, called polysaccharides, from Group A meningococci to a protein carrier, which activates a much broader part of the immune system, resulting in stronger, longer-lasting protection. Conjugate vaccines also prevent people from carrying the bacteria and passing it to other people, helping to protect unvaccinated individuals via herd immunity.

The trouble is, there are five further serogroups of N. meningitidis that can cause epidemics: B, C, Y, W and X. While conjugate vaccines are available that protect against Groups B, C, Y and W, these are unaffordable for routine use in most lower-income countries – although they have been used during outbreaks. Groups C, W and X are also a growing problem in sub-Saharan Africa, and no existing vaccine protects against X.

"We need vaccines to prevent and respond to epidemics caused by these other groups," said Prof Caroline Trotter, an infectious disease epidemiologist at the University of Cambridge and Imperial College London, UK, and Chair of the Meningitis Research Foundation's Scientific Advisory Panel.

2. MenFive protects against the five leading causes of epidemic meningitis in sub-Saharan Africa

In July 2023, the World Health Organization prequalified a new meningococcal conjugate vaccine, Men5CV (MenFive), that protects against the five serogroups responsible for almost all epidemic meningitis in sub-Saharan Africa: Groups A, C, Y, W and X.

"With outbreaks of infectious diseases on the rise worldwide, new innovations such as MenFive are critical in helping us fight back," said Dr Tokunbo Oshin, Director of High Impact Countries at Gavi, the Vaccine Alliance. "Thanks to vaccines, we have eliminated large and disruptive outbreaks of meningitis A in Africa: now we have a tool to respond to other meningococcal meningitis serogroups that still cause large outbreaks resulting in long-term disability and deaths."

Importantly, the vaccine is temperature stable, which will make it easier to reach and protect remote communities with poor health infrastructure.

Its introduction is expected to build on the impact of the MenAfriVac vaccine against Group A meningococcus and is considered a critical step towards the goal of eliminating epidemic meningitis by 2030.

3. It is more affordable than existing multivalent meningococcus vaccines

The vaccine is the result of a 13-year development collaboration between Serum Institute of India and PATH, with funding from the UK government's Foreign, Commonwealth and Development Office. "Because some of the development costs were shared, and the manufacturers committed to creating meningitis vaccines for use in Africa, this makes it more affordable than vaccines produced by pharmaceutical companies in the Global North," said Trotter.

With an anticipated cost of around US$ 3 per dose, the MenFive vaccine is expected to be more accessible to meningitis belt countries than existing meningococcal conjugate vaccines that protect against multiple serogroups. This means that countries are more likely to be able to include it in their routine immunisation programs.

4. One dose is expected to provide strong protection against meningococcal infections

Although the efficacy of the MenFive vaccine is currently unknown, it was licensed on the basis of safety and immunogenicity (immune response) data in infants, which suggested it was "non-inferior" to the existing quadrivalent MenACWY-TT vaccine that has been in use in the US since 2005, with no notable safety concerns. An earlier study also found that it was found safe and immunogenic for healthy 2- to-29-year-olds in Mali and Gambia, and that 97% of people who received the MenFive vaccine developed a strong immune response against Group X meningococci.

"I think we can be confident that this vaccine will work, because we know that MenAfriVac, which is made by the same company, is very effective, and we know that other multivariant meningococcal conjugate vaccines are highly effective," said Trotter.

5. Widespread preventive use of the vaccine is the best strategy to prevent outbreaks from occurring

In February 2024, Nigeria became the first country to receive doses of the MenFive vaccine from the Gavi-funded emergency stockpile, which ensures rapid supply of vaccines to outbreaks of meningitis, yellow fever, cholera and Ebola for lower-income countries. The doses will be used to respond to an ongoing meningococcus C outbreak in Nigeria, targeting around one million children.

However, "although it is being used for the first time in the Nigeria outbreak response, it is really going to have the biggest impact when it's used in preventive campaigns as recommended by the World Health Organization's Strategic Advisory Group of Experts on Immunization (SAGE) committee," said Trotter.

WHO has advised all countries in the meningitis belt to introduce the new vaccine into their routine immunisation programmes, with a single dose scheduled at 9 to 18 months of age. In high-risk countries, and those with high-risk districts, WHO has recommended further catch-up campaigns targeting all 1- to 19-year-olds. Countries that are already using the MenAfriVac vaccine against Group A should start switching to MenFive, WHO said.

Gavi will support these efforts by helping to fund the purchase of MenFive doses for introduction into routine immunisation schedules and catch-up campaigns for low-income countries at high risk of epidemic meningitis, in addition to outbreak response. Applications for such support are expected to open during 2024.

Although the vaccine is primarily designed to prevent epidemics of meningitis in African countries, it may find further uses elsewhere. "For example, it may also be useful for Hajj pilgrims who need to be vaccinated to protect them against meningococcal disease," Trotter said.

This article was originally published on VaccinesWork.

Author: Linda Geddes

Date: 25 March 2024

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