AuthorisedTherapeutic confirmatory (Phase III)Interventional

C4931004 - A Phase 3, Randomized Double-Blind Trial to Evaluate the Safety, Tolerability, and Immunogenicity of a Catch-Up Vaccination Regimen of a Multivalent Pneumococcal Conjugate Vaccine in Healthy Children and Adolescents

Pneumococcal bacteria can cause serious illnesses, including chest infections (pneumonia), ear infections, and meningitis. Vaccines help train the immune system to defend against these germs. This trial is testing a jab called Prevenar 20 in healthy children and young people aged between 15 months and 17 years. Prevenar 20 is designed to protect against 20 different strains of pneumococcal bacteria. The study is checking a 'catch-up' schedule for children who may not have had this newer jab when they were younger. Doctors want to see what temporary side effects occur—such as arm soreness or a mild fever—and how well the body produces protective antibodies. Taking part is voluntary. The study helps doctors learn whether this vaccine can safely offer broader protection to children and young people in the UK and worldwide.

At a glance

Status

Authorised

Phase

Therapeutic confirmatory (Phase III)

Sponsor

Pfizer Inc.

Enrolment target

480

Start

28 Sep 2026

Pneumoccoccal Immunisation

What is this study about?

Pneumococcal disease is an infection caused by bacteria called Streptococcus pneumoniae. These bacteria can cause common childhood problems like painful middle ear infections, but they can also lead to life-threatening conditions like severe pneumonia, blood poisoning (sepsis), and meningitis. Vaccines have made these illnesses much rarer, but scientists are always working to protect against more bacterial strains.

This clinical trial is testing Prevenar 20 in children and teenagers who are between 15 months and 17 years old. Prevenar 20 covers 20 different types of pneumococcal bacteria. In this study, doctors are looking at a 'catch-up' programme. This means giving the jab to older babies, children, and teenagers who did not receive this specific vaccine during their routine baby immunisations.

The trial is a Phase 3 study, which means the vaccine has already passed early safety checks in smaller groups. Researchers will monitor participants closely to check for common reactions, like redness or soreness where the injection was given, or mild symptoms like tiredness and fever. They will also take blood samples to measure antibody levels, which show how strongly the immune system has responded.

Research like this is vital for public health bodies, such as the NHS. It gives doctors the evidence they need to decide if new vaccines should be added to regular vaccination schedules to keep children protected as they grow.

Key takeaways

Tests the Prevenar 20 vaccine in healthy children and teenagers aged 15 months to 17 years.
Aims to protect against 20 different strains of bacteria causing pneumonia, ear infections, and meningitis.
Monitors common mild reactions like soreness, fever, and tiredness to confirm safety.
Checks blood samples to see how strongly the immune system responds to the vaccine.
Participation is voluntary, and you can withdraw your child at any point without affecting their NHS care.

Who may be eligible?

This trial is open to healthy children and teenagers aged from 15 months up to 17 years old. The study groups children into different age brackets: young toddlers aged 15 to 23 months, and older children and teenagers aged 2 to 17 years.

To take part, children must generally be in good health. A child might not be able to join if they have a weakened immune system, a long-term serious medical condition, or a known severe allergy to any vaccines. Children who have recently had certain other vaccines or treatments may also need to wait.

A doctor from the study team will review your child's medical history and current health with you to make sure it is completely safe for them to take part before any jabs are given.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

My child is aged between 15 months and 17 years old.
My child is in generally good health.
My child does not have a known severe allergy to vaccines.
My child does not have a condition that severely weakens their immune system.
We are willing to attend clinic visits and record any mild symptoms in a daily diary.

Answer every question to see your result.

What does participation involve?

Taking part usually involves a few visits to a study clinic over several months. During the first visit, the study team will explain everything, answer your questions, and ask for your written consent (and your child's agreement if they are old enough). Your child will have a quick health check and receive the study vaccine as a small injection, usually in the upper arm or thigh.

After the injection, parents or young people will be asked to track any symptoms at home for about a week using an electronic diary or app. This includes noting things like mild fever, redness at the injection site, or tiredness. The team will arrange follow-up visits or phone calls to check on your child's health and will take small blood samples to see how well their immune system is responding. The trial team will support you throughout the study, which typically lasts around six months.

Potential risks and benefits

Your child might benefit by gaining protection against 20 strains of pneumococcal bacteria, though this cannot be guaranteed. The study also helps improve vaccine options for other children in the future. The most common risks are mild and temporary reactions from the injection, such as redness, swelling, or pain where the needle went in, as well as mild fever, headache, or irritability. Blood tests may cause brief discomfort or slight bruising. Serious allergic reactions are very rare, and medical staff are always present to manage them. You can withdraw your child from the study at any time without giving a reason, and it will not affect their normal NHS care.

Locations (2)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

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Unverified
Poland
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Unverified
Finland

Common questions

What is the Prevenar 20 vaccine?

Prevenar 20 is a vaccine designed to protect against 20 different types of pneumococcal bacteria that can cause serious chest, ear, and brain infections.

Will having this jab hurt my child?

Like any routine childhood jab, the injection may cause a brief pinch or sting. The arm or thigh might feel a little sore or look red for a few days afterwards.

Why is this called a 'catch-up' study?

It is called a catch-up study because it tests the vaccine in children who are older than the usual age for early baby jabs, ensuring they can still get protection.

Does it cost anything to take part?

No, taking part is free. The study vaccine and all trial-related appointments are provided at no cost, and travel expenses are often reimbursed.

Can we stop taking part if we change our minds?

Yes. Taking part is completely voluntary. You or your child can decide to leave the trial at any point, and your standard NHS medical care will continue as normal.