Meningitis B Explained: Symptoms, Spread, and Vaccine Coverage

In medical terminology, the suffix “-itis” refers to inflammation. Therefore, meningitis refers to inflammation of the meninges—the protective membranes surrounding the brain and spinal cord. 

Meningitis is a serious, life-threatening condition, currently in the spotlight due to a recent outbreak of invasive meningococcal disease in Kent, with 21 confirmed cases and, sadly, 2 resulting deaths since March.

As we remain on high alert following the COVID-19 pandemic, the situation has understandably raised concerns for many: Does this mean another pandemic is imminent? What symptoms should I look out for? Am I protected by my childhood vaccinations?

In an era of social media reporting and anecdotal storytelling, it can be difficult to separate information from speculation, leading to unnecessary and unhelpful alarm. However, through this article, readers can gain a science-based understanding of the emerging situation and make sense of the information available.

The pathogen behind meningitis cases in Kent

Meningitis has many causes, each with a distinct distribution and trajectory (Table 1).

Table 1: Causative pathogens, with associated disease progression, of meningitis.

The cluster of cases in Kent has been classified as bacterial, caused by Neisseria meningitidis. Many headlines have described a “meningitis B outbreak” because the specific causative strain falls within the category of group B meningococci.

It is estimated that between 5–10% of the population are asymptomatic carriers of N. meningitidis, and of those carriers, less than 1% will develop invasive illness.

Who remains asymptomatic, and who develops invasive disease? 

For invasive diseases such as meningitis to occur, N. meningitidis must overcome various barriers: the epithelial lining of the nasopharynx, the vascular endothelium, and the blood-brain barrier. Each of these barriers is highly complex. The nasopharyngeal barrier, for example, is inherently dynamic to prevent invasion by such microorganisms, acting as one of the body’s first lines of defense. Additionally, within serogroups, different strains exist, and each exhibits distinct behaviors.  

Although we do understand how N. meningitidis spreads and which factors influence susceptibility to invasive disease, enabling identification of high-risk individuals, the combined complexity of host barriers and strain-specific behaviors leaves progression from asymptomatic carriage to invasive disease unpredictable.

How does N. meningitidis spread?

N. meningitidis can be transmitted via inhalation of airborne respiratory and saliva droplets, and is often spread from asymptomatic carriers. Teenagers and young adults exhibit the highest carriage rates, largely attributed to social behaviors such as living in university dormitories, attending crowded parties, kissing, and vaping, all of which can facilitate transmission. The high prevalence in this group directly correlates with an increase in invasive cases.

Infants, immunocompromised populations, and the elderly also face increased risk of invasive disease due to weaker immune systems.

What are the key signs of meningitis?

The classic clinical triad of meningitis symptoms is fever, neck stiffness, and altered mental status (confusion). However, less than half of bacterial meningitis cases present in this way. Other signs include:

·       Headache

·       Light sensitivity

·       Nausea and vomiting

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·       Seizures

·       Severe sleepiness

·       A rash that does not fade when glass is pressed against it

Additional signs in infants include irritability, poor feeding, pale or blotchy skin, and bulging in the fontanelle—the soft spot at the top of the head.

Bacterial meningitis is associated with high mortality, of up to 100% in untreated individuals. With treatment, this figure drops to 10–20%.

Regarding treatment, Prof. Andrew Smith, honorary consultant microbiologist at the University of Glasgow, told the Science Media Center: “These strains are sensitive to antibiotics used for treatment or prevention of meningococcal infection.”

With 21 confirmed cases, what made this an outbreak?

According to the World Health Organization, an outbreak is “the occurrence of cases of disease in excess of what would normally be expected in a defined community, geographical area, or season”.

So, what defines the events in Kent as an outbreak?

To put into context, England typically reports less than 400 cases of invasive meningococcal disease annually, which equates to an average of 6–8 cases per week, distributed geographically across the country. Therefore, the confirmation of 15 cases within 48 hours, all linked to one location, met the definition.

Epidemiological testing and strict notification criteria confirmed the spike in cases as a genetically distinct outbreak. Prof. Martin Maiden, professor of molecular epidemiology at the University of Oxford, told the Science Media Center that: “The isolated bacterium that has been sequenced is very closely related to other meningococci we have seen before, but it is distinct.”

“If you think of Russian dolls, this is a unique Russian doll inside other known Russian dolls.” — Prof. Martin Maiden

The strain of N. meningitidis implicated in the outbreak has been circulating for five years, so it's crucial to identify and investigate factors that may have contributed to the sudden rise in cases: evolutionary changes in the bacteria, variations in population immunity, or specific conditions that drove transmission.

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Bacterial meningitis is life-threatening and rapidly progressive. Therefore, the emerging situation necessitated a quick response for both individual patients and the wider community.

The declaration of an outbreak is not simply a definitional exercise or done to invoke fear. It serves to facilitate immediate public health intervention, including:

• Targeted intervention: Antibiotic prophylaxis was offered to close contacts of confirmed or probable cases to limit spread and treat potential cases.
• Population protection: The MenB vaccine was offered to eligible individuals to reduce disease severity if contracted.
• Enhanced surveillance: Statutory reporting of all clinically diagnosed cases followed by laboratory analysis to confirm and characterize the implicated strain supports surveillance.

What makes the outbreak in Kent different from COVID-19?

The transmission of the two diseases is distinct. N. meningitidis is a bacterium that often lives harmlessly within hosts, requiring prolonged close contact for transmission. On the other hand, SARS-CoV-2 spreads easily through respiratory aerosols and continues to account for as many cases weekly as are typically seen in an entire year for N. meningitidis.

The response following confirmed meningitis cases was worlds apart from the experiences during the emergence of SARS-CoV-2—an unknown entity at the time, untestable and untreatable—that resulted in a global pandemic.

Definitive steps guided by existing clinical protocols and national guidelines were taken to successfully contain the meningitis B outbreak.  Although the volume of cases was unprecedented, clinicians recognized the presentation, laboratories could perform diagnostics, and pharmaceutical interventions for both treatment and prevention were available. These factors were key to halting the spread and account for the successful containment of the outbreak.

Not all meningitis vaccines cover meningitis B

Different meningitis vaccines cover different serogroups, and vaccination schedules have changed in the last few decades, making it difficult to understand what protection an individual may or may not have (Table 2).

Table 2: Table summarizing meningococcal bacteria-specific vaccination schedules.

The purpose of a vaccine is to provide a person with immunity to an infectious agent. Vaccines do not prevent infection altogether, but they do reduce severe illness and limit spread.

The United Kingdom was the first country to introduce the MenB vaccine into the national childhood immunization program. The vaccine is given to babies, the most at-risk group for contracting and becoming severely unwell from meningococcal group B-related disease.

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At the same time, MenACWY vaccination was rolled out among teenagers, aiming to confer protection against the strains this group is more likely to carry and transmit.

As the MenB vaccine was only introduced into the immunization program in 2015, it is not expected that students over 18 years old studying at the University of Kent will have received it unless they had specific risk factors or paid for private vaccination.

As part of the outbreak response, the MenB vaccine was offered to individuals meeting strict eligibility criteria. Smith told the Science Media Centre that: “The whole genome data has provided information that predicts this strain is covered by both the MenB vaccines.”

While there have been calls for a wider, national roll-out of the vaccine following the outbreak, the official guidance remains that the risk to the public is low.

Continued vigilance

While the meningitis B outbreak appears to have passed its peak, the knock-on effects remain evident. NHS emergency departments reported their busiest month on record in March, with almost 2.5 million attendances, an increase driven in part by the outbreak.

The increase in attendance may reflect heightened public awareness of key warning signs and symptoms brought to their attention by public health communications, as well as a reduced threshold for health-seeking behavior, potentially influenced by concern. It is important to maintain this same level of awareness—not alarm—moving forward.

The situation is being effectively managed and monitored. Invasive bacterial meningococcal disease is a serious but rare occurrence. Most people who carry N. meningitidis will never become unwell, and effective vaccines and treatments already exist for those at risk or with suspected/confirmed cases.

“There is still a lot of uncertainty, but I am cautiously optimistic that this will turn out to be a rare, chance, event.  So far, we haven’t seen secondary cases unlinked with the club.  But we need to remain aware of the possibility of further cases.” — Prof. Martin Maiden