Bacterial meningitis in children: What to know about meningococcus, pneumococcus, and HiB

Meningococcus, pneumococcus and Haemophilus influenzae type B (HiB) are three of the most common forms of bacterial meningitis, which kills one in six people who get it

Meningitis is the infection and inflammation of the protective tissues around the brain and spinal cord (the meninges). It has various causes – but most commonly, it’s caused either by bacteria or virus. The most dangerous type, bacterial meningitis, causes more than half of all meningitis deaths globally.

Vaccination has made meningitis rarer than it used to be. But it still causes significant illness and death, especially in people who are unvaccinated. Globally, it’s estimated that someone develops meningitis every 15 seconds.

The consequences can be devastating. According to the World Health Organization, around one in six people who get bacterial meningitis die from it. For those who survive, around one in five have long-term effects, which can include seizures, paralysis, loss of hearing, cognitive impairment or vision problems.

Meningitis symptoms can include fever, stiffness of the neck, headaches, light sensitivity, confusion, and nausea. In infants, symptoms also can include crying weakly, not feeding as normal, or being more irritable or drowsier than usual. The soft spot on their head may also start to bulge. In any of these cases, it is important to seek emergency medical attention immediately.

Several different types of bacteria can cause bacterial meningitis. Three of the most common are Neisseria meningitidis (meningococcus), Streptococcus pneumoniae (pneumococcus) and Haemophilus influenzae type B (HiB). They are most dangerous for children and adolescents.

Today, there are vaccines for all three bacterial strains – usually given in infancy to protect children when they are at their most vulnerable to the disease.

The fourth most common type of bacterial meningitis, Streptococcus agalactiae (group B streptococcus), does not yet have a commercially available vaccine.

Together, these available vaccinations have contributed to a significant global decline in meningitis cases and deaths. However, vaccination rates against meningitis-causing bacteria have stagnated or declined in recent years – and deaths from some types of meningitis have risen. After declining in 2020 and 2021, for example, meningococcal disease rose in 2022 in the European region. The rate of meningococcus was the highest in infants under one.

Across Europe and Central Asia, the latest 2024 data indicates that only about 88 per cent of infants have received the three recommended doses of a pneumococcal-conjugate-containing vaccine. The countries with the lowest coverage include Germany (75 per cent of children covered), North Macedonia (72 per cent), Slovenia (56 per cent) and Azerbaijan (52 per cent). In some countries, rates have declined from pre-pandemic levels: in 2018, 82 per cent of children in Germany, 70 per cent of children in Azerbaijan and 60 per cent of children in Slovenia received all three doses. (North Macedonia’s data were unavailable in 2018).

Read on to find out more about the different types of bacterial meningitis, how they can be prevented, and how the vaccinations that prevent the three main types – Haemophilus influenzae type B (HiB), Neisseria meningitidis (meningococcus) and Streptococcus pneumoniae (pneumococcus) – really work.

Haemophilus influenzae type B (HiB) and the HiB vaccine

For decades, meningitis caused by Haemophilus influenzae type B (HiB) was the most common cause of meningitis death in children. Even today, around 9 in 10 people who contract HiB are under the age of five. More than half of those who contract HiB get meningitis.

This HiB-causing strain of bacteria also can cause deadly infections of the blood (septicemia) and lungs (pneumonia), among other infections.

Even with prompt treatment by antibiotics, up to one in five children infected with HiB die. For those who survive, around 3 or 4 of every 10 children will experience neurological disability and/or hearing loss.

HiB is spread through respiratory droplets, such as sneezing or coughing. It can also be passed to the fetus in pregnancy. This means it can spread easily within households or other enclosed settings, like daycares or schools.

While HiB vaccines have existed since the 1970s, the biggest decline was largely thanks to a major breakthrough in vaccine technology in the 1980s.

Before this, the first HiB vaccines had a limited impact in children – the highest-risk group – because children mounted weak immune responses. The kind of antigen being used also activated B cells, but not T cells, which meant that the vaccine failed to generate long-term protection.

In 1987, however, scientists developed the first-ever conjugate vaccine – which was for HiB. This type of vaccine linked the polysaccharide antigen to a protein carrier, which triggered a T-cell-dependent response.

The innovation provided stronger immune responses in infants and children and long-lasting protection. It also reduced how much the bacteria replicated in the passages of the nose and throat, lowering the likelihood of transmission. This meant that someone who was vaccinated and still contracted the bacteria was less likely to pass it on to someone else.

After the conjugate HiB vaccine was rolled out, countries saw their overall incidence of HiB plummet by 97 per cent or more. Because of how it protected not only vaccinated people, but kept them from passing it on, even people who did not receive the vaccine were protected by its effects.

In Europe, European countries began introducing the conjugate HiB vaccine into national programmes from 1989. It is now part of the national programme in every EU country.

Meningococcus and the meningococcal vaccine

Meningococcal meningitis (meningococcus) is caused by the bacterium Neisseria meningitidis. Twelve groups of this bacterium – called serogroups – have been identified. The vast majority of meningococcus cases are caused by six: serogroups A, B,C, W135, X and Y.

In addition to meningitis, these bacteria can cause sepsis (blood infection) and severe hypotension (low blood pressure), which can rapidly cause death if untreated.

As with other meningitis-causing bacteria, Neisseria meningitidis lives and replicates in the nose and throat passages. It is spread through respiratory secretions, like saliva. Infants, young children, and adolescents are the most vulnerable age groups.

Outbreaks are more likely to occur in crowded or high-risk settings, such as university dorm rooms, refugee camps, military barracks, or mass gatherings, like sports events.

Even when an infected person receives prompt and advanced medical treatment, the risk of death is high - up to one in five.  Of those who survive, about 7 in every 100 have long-term neurological impairment.

Meningococcus remains a threat, particularly in regions with lower vaccination coverage. In the highest-incidence region in the world, Africa, more than 1,000 people contract the bacterium out of every 100,000 per year. In Europe, where vaccination is more widespread, only up to 10 people do.

The first meningococcal vaccines were developed in 1969, targeting serogroups A and C. Later trials found that when these two vaccines were administered together, they were as effective — or even more effective — than when given separately. In the 1980s, additional vaccines were developed to cover serogroups Y and W135.

As with the first vaccines for HiB, these first meningococcal vaccines had a limited impact in children. A major breakthrough came in the 1990s, when scientists developed conjugate vaccines for meningococcus – just a few years after the first conjugate vaccine was developed for HiB in 1987. This new type of vaccine provided stronger immune responses in infants and children, long-lasting protection, and herd immunity effects (reduced bacterial carriage and transmission).

Today, meningococcal vaccines include:

• Multivalent polysaccharide conjugate vaccines (MMCVs): Protect against 4–5 serogroups (A, C, W, Y, and X).
• Protein-based vaccines: Protect against serogroup B.
• Combination vaccines: Combine protein-based B vaccines with 4-valent conjugate vaccines (A, C, W, Y).

These vaccinations have proved highly effective. In England, Wales and the Netherlands, for example, prevalence of meningococcus serogroup C declined by more than 98 per cent in age groups that were targeted by the vaccine. Because the vaccine also reduces bacteria’s ability to replicate in the nasal and throat passages, and to be passed on to others, it also protected people who did not receive the vaccine: even in age groups that were not immunized, prevalence of meningococcus fell 90 per cent.

Similarly, in the so-called “African meningitis belt”, serogroup A historically caused 80–85% of meningitis epidemics; after the  meningococcal A conjugate vaccine (MenAfriVac) was rolled out in 2010, serogroup A epidemics were all but eliminated.

Pneumococcus and the pneumococcal vaccine

Pneumococcal disease is caused by a bacterium called Pneumococcus, or Streptococcus pneumoniae. This is the single leading cause of both bacterial meningitis and of severe pneumonia worldwide. The bacterium also can cause other infections, such as bacteraemia – when it gets into the blood.

Like the other diseases caused by the bacteria here, it can be deadly. Around 294,000 children died of pneumococcal infections in 2015 alone. In low- and middle-income countries, up to one out of every two children infected with pneumococcus die. In high-income countries, around 1 in 20 children infected die of pneumonia, 1 in 12 die of meningitis and 1 in 30 die of bacteraemia.

The most vulnerable group to the bacterium are children, with around 9 in 10 people who get pneumococcus under the age of five.

This bacteria is spread through respiratory droplets, like when someone coughs or sneezes. In addition to meningitis, it can cause other types of infections, including infections of the lungs (pneumonia) and the blood (bacteremia).

There are more than 90 different types of this bacterium, which has made developing a fully preventative vaccine challenging.

In 2000, the first vaccine that provided immunization against the seven most common types was trialled on more than 37,000 infants in the United States. It was found to be more than 95% effective, meaning that infants who were fully vaccinated were 95% less likely to get the disease than infants who were not.

As with the other vaccines, it also protected those who weren’t vaccinated. Because it prevents the bacteria from replicating in the infected person’s mucus and nose, they are less likely to infect other people. This offers herd protection.

These pneumococcal conjugate vaccines (PCVs) are now part of immunization programmes in more than 190 countries.

As a result, deaths and infections by pneumococcus have declined. In 2000, some 695,200 children under the age of five died worldwide from pneumococcus. In 2015, after vaccines were rolled out to many of the most affected countries, that had more than halved, with 317,000 deaths of children under five. More than 8 in 10 of these deaths were from pneumococcal pneumonia and 1 in 10 were from pneumococcal meningitis.

But as pneumococcal vaccines have defended us against an ever wider range of serogroups, other strains have become more prevalent. As a result, the vaccine has evolved since then to protect against an even broader range of strains. Some, with protection against up to 20 strains, have been approved in the US and Europe as of 2021.