Meningococcus

Meningococcus is a bacterium that can cause severe infections such as meningitis and sepsis. Anyone of any age can contract meningococcal infections, but cases are most common among young children and teenagers. The bacterium spreads through respiratory droplets—when an infected person coughs or sneezes. Close contact, such as living or eating in the same space, increases the likelihood of transmission.

Often, infection results in asymptomatic or transient throat colonization that clears within a few months without requiring any intervention. Approximately 5–10% of the population carries meningococcal bacteria in their throat and can spread it to others. For a small fraction of those infected, the disease can progress to a serious infection. While most cases are isolated, meningococcus has the potential to cause widespread epidemics.

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Life-Threatening Meningococcal Infection

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Meningococci are classified into 12 capsule-based groups (serogroups), with groups A, B, C, W, X, and Y being the most significant. In Finland, the most common disease-causing serogroups are B, C, and Y.

Infections caused by meningococcus can be rapidly severe. Meningitis, bacteremia (bloodstream infection), or sepsis may occur separately or together. Symptoms often develop and worsen quickly, with a patient’s condition deteriorating within hours to a level requiring intensive care. Without treatment, meningococcal disease is nearly always fatal. Even with prompt intravenous antibiotics and intensive care, about one in every ten patients dies.

Among survivors of severe disease, up to one-third are left with permanent disabilities, such as hearing loss or limb amputations resulting from septic tissue damage.

Common symptoms include:

• Sudden high fever
• Headache
• Stiff neck
• Hypersensitivity to light
• Rapidly deteriorating condition
• Petechial rash (small pinpoint hemorrhages on the skin)

Nausea, vomiting, or confusion may also occur. In young children, signs can be subtle—such as lethargy, labored breathing, or irritability when touched. If meningococcal infection is suspected, immediate hospitalization is necessary.

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Meningococcal Vaccines

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Meningococcal vaccines are safe and effective. In Finland, meningococcal disease prevalence is low, so vaccination is focused on risk groups. In contrast, several European countries include meningococcal vaccines in their national immunisation programmes due to higher local disease rates.

Serogroups A, B, C, W, and Y are responsible for disease. Different vaccines offer protection against one or more of these serogroups.

Conjugate meningococcal vaccines covering four serogroups (ACWY) are now primarily used—they provide better and longer-lasting protection, especially in young children under two years. In many countries, these are part of routine immunization schedules for infants, adolescents, or people in high-risk groups.

In Finland, two ACWY conjugate vaccines are available: one is approved for individuals aged two years and up, and the other for those aged six weeks and older, including adults.

Additionally, protein-based vaccines targeting serogroup B have been developed and are available. One is approved for children from two months of age and older, and the other for individuals aged ten years and above.

FVR has extensive experience conducting research on both the multivalent ACWY vaccines and the serogroup B protein vaccines. The goal remains to develop a broad-spectrum meningococcal vaccine that protects against the five most common disease-causing groups. Even as new vaccines are developed, more research is still needed on the duration of protection and booster timing for existing vaccines.