Immunology and vaccination

Meningitis and vaccination: how MenB and MenACWY vaccines protect us

Meningitis can progress rapidly and may become life-threatening within hours. Learn how the MenB and MenACWY vaccines work with the immune system, who should receive them and why vaccinated people must still recognise the warning signs.

Vaccination is one of the most effective ways to reduce the risk of meningococcal meningitis and sepsis. In the UK, two important meningococcal vaccines are used: MenB and MenACWY. Although both protect against Neisseria meningitidis, they target different groups of the bacterium and use different vaccine technologies.

What is meningitis?

Meningitis is inflammation of the meninges—the protective membranes surrounding the brain and spinal cord. It can be caused by bacteria, viruses, fungi and, much less commonly, parasites. Certain medicines and inflammatory conditions can also cause non-infectious meningitis.

Viral meningitis is often less severe than bacterial meningitis, although this is not always the case. Bacterial meningitis is a medical emergency because it can progress quickly and cause sepsis, brain injury, hearing loss, seizures, limb loss or death.

What is meningococcal disease?

Meningococcal disease is caused by the bacterium Neisseria meningitidis, also called meningococcus. The bacteria can live harmlessly in the back of the nose and throat. This is known as carriage, and many carriers never become unwell.

The bacteria spread mainly through prolonged close contact and respiratory secretions—for example, through coughing, kissing or living closely with other people. In rare cases they cross the lining of the throat and enter the bloodstream or the tissues surrounding the brain and spinal cord.

Meningococci are classified into groups according to their outer polysaccharide capsule. Groups B, C, W and Y are particularly relevant in the UK, while group A remains important in some parts of the world.

MenB and MenACWY: what is the difference?

How does the MenACWY vaccine activate immunity?

MenACWY is a conjugate vaccine. It contains purified components from the polysaccharide capsules of meningococcal groups A, C, W and Y. Each polysaccharide is joined to a carrier protein.

This conjugation is immunologically important. Polysaccharides alone may produce a relatively weak or short-lived response, particularly in young children. Attaching them to a protein enables antigen-presenting cells and helper T cells to support a stronger B-cell response.

• B cells produce specific antibodies against the meningococcal capsule.
• Some activated B cells become long-lived plasma cells or memory B cells.
• If the bacteria are encountered later, immune memory supports a faster response.
• Reduced bacterial carriage can contribute to indirect protection in the community.

MenACWY contains no live meningococcal bacteria and cannot cause meningococcal disease.

How does the MenB vaccine activate immunity?

Developing a group B vaccine was more difficult. The MenB capsule resembles certain structures found naturally in human tissues and does not provide a suitable target for a conventional capsule-based vaccine.

Instead, the MenB vaccine used routinely in the UK contains selected proteins found on the surface of group B meningococci. Vaccination encourages B cells to produce antibodies that recognise these bacterial proteins. The antibodies bind to the bacterial surface and work with the complement system to damage and destroy the bacteria before invasive disease develops.

Who is offered the MenB vaccine in the UK?

Babies are routinely offered three MenB doses through the NHS childhood vaccination programme:

Timely vaccination matters because babies and young children are among those at greatest risk. If a child has missed a dose, parents should contact their GP surgery because catch-up vaccination may be available.

A temporary NHS MenB programme is also operating during 2026–27 for specified young people, including an eligible age cohort and eligible first-time university or further-education students living in relevant accommodation. Two doses are important for protection. Eligibility and deadlines should be checked using the latest NHS guidance.

Who is offered the MenACWY vaccine?

MenACWY is routinely offered to teenagers, usually in school Year 9, at approximately 13 or 14 years of age. Anyone who missed it at school can normally receive NHS catch-up vaccination up to their 25th birthday.

It may also be recommended for:

• People with particular immune-system disorders
• People without a functioning spleen
• Laboratory workers with occupational exposure to meningococci
• Some close contacts of a confirmed case
• Travellers visiting countries where particular meningococcal groups are more common
• Pilgrims travelling to Hajj or Umrah, where documented vaccination may be required

Travel requirements and schedules can change. Advice should be obtained well before departure.

Why are complement disorders especially important?

The complement system is a network of immune proteins that helps antibodies eliminate microbes. It is particularly important for destroying meningococcal bacteria.

People with inherited or acquired complement deficiencies—especially those affecting the terminal complement pathway—have a substantially increased risk of invasive or recurrent meningococcal infection. Risk is also increased in people receiving complement-inhibiting medicines such as eculizumab or ravulizumab.

Vaccination does not provide complete protection while complement activity is inhibited. Patients should follow the plan provided by their immunology, haematology or specialist team. People with absent or poorly functioning spleens may also require both meningococcal vaccines and additional protection against other encapsulated bacteria.

Can immunocompromised patients receive these vaccines?

MenB and MenACWY are non-live vaccines. They can generally be administered to people with weakened immune systems, although the immune response may be less complete than in an immunocompetent person.

Where clinically possible, vaccination may be timed before planned immunosuppressive treatment, complement-inhibitor therapy, elective splenectomy, certain cancer treatments or transplantation procedures. Essential treatment must not be delayed without specialist advice.

Vaccine allergy and anaphylaxis

Most people with allergies can safely receive MenB and MenACWY vaccines. Asthma, eczema, hay fever, food allergy, an allergy to an unrelated medicine or a family history of allergy is not normally a reason to avoid vaccination.

The main allergy-related reasons not to receive a particular vaccine are:

• Previous anaphylaxis to a dose of the same vaccine
• Confirmed anaphylaxis to one of the vaccine’s ingredients

Fever, fatigue, local pain and swelling are expected inflammatory effects and do not usually indicate an IgE-mediated allergy. By contrast, immediate breathing difficulty, throat or tongue swelling, widespread hives, collapse or a marked fall in blood pressure requires medical assessment before another dose is given.

When necessary, an allergy specialist can examine the timing and features of the reaction, review the complete ingredient list, consider other explanations and advise whether supervised vaccination is appropriate. Anaphylaxis after vaccination is very rare, and vaccination teams are trained to recognise and treat it promptly.

Expected side effects

Most reactions are mild and resolve within one or two days. Fever is particularly common when MenB is given to babies alongside other routine vaccines. The NHS recommends infant paracetamol after MenB vaccination at 8 and 12 weeks; parents should follow the instructions provided by their vaccination team and use a product suitable for the baby’s age.

How effective are the vaccines?

Both vaccines provide important protection, but neither prevents every case. MenB protects against many group B strains, while MenACWY protects only against the four groups in its name. Neither vaccine prevents viral meningitis or every other bacterial cause.

Not everyone develops the same level or duration of immunity. Responses may be reduced in some people with immune disorders or during immunosuppressive or complement-inhibiting treatment. Vaccinated people must therefore remain alert to symptoms.

Can meningitis occur after vaccination?

Yes. This does not necessarily mean that a vaccine has failed. Meningitis can be caused by viruses, other bacteria and meningococcal groups not covered by the vaccine. A vaccinated person can also occasionally develop infection from a strain not adequately matched by the vaccine, or because their immune response was incomplete.

Vaccination substantially reduces risk, but it never replaces urgent medical assessment when symptoms suggest meningitis or sepsis.

Key messages

Medical disclaimer: This article provides general information and does not replace individual medical advice. Vaccination programmes and travel requirements may change. Please consult your GP, vaccination service or specialist clinical team about personal eligibility and scheduling. Information reviewed September 2026.

References and further information

1. NHS: MenB vaccine for children
2. NHS: MenACWY vaccine
3. NHS: Vaccinations and when to have them
4. NHS: Meningitis symptoms and emergency advice
5. UK Health Security Agency: Meningococcal disease—Green Book, Chapter 22
6. World Health Organization: Vaccines and immunisation