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Study on the Safety and Immune Response of a 21-Valent Pneumococcal Conjugate Vaccine in Healthy Infants and Toddlers

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying a vaccine for preventing infections caused by the bacteria *Streptococcus pneumoniae*, commonly known as pneumococcal disease. This disease can lead to serious infections like pneumonia, meningitis, and bloodstream infections, especially in young children. The study will compare two vaccines: a new 21-valent *Pneumococcal Conjugate Vaccine (PCV21)* and an existing 15-valent vaccine called *Vaxneuvance*. The term "valent" refers to the number of different types of bacteria the vaccine can protect against. The purpose of the study is to see if the new vaccine is as effective or better than the existing one in producing a strong immune response in infants and toddlers.

Participants in the study will receive either the new *PCV21* vaccine or the *Vaxneuvance* vaccine. The vaccines are given as a series of injections into the muscle. The study will monitor the immune response by measuring the levels of antibodies, which are proteins the body makes to fight infections. The study will also check for any side effects or reactions to the vaccines. The goal is to ensure that the new vaccine is safe and effective for young children.

The study will last for several months, with follow-up visits to check the health and immune response of the participants. The researchers will look at how well the vaccines work against the different types of pneumococcal bacteria included in the vaccines. This information will help determine if the new vaccine can provide better protection against pneumococcal disease in children. The study will also track any immediate or long-term side effects to ensure the safety of the vaccines.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, the participant will be assessed to ensure they meet the eligibility criteria. This includes being between 42 to 112 days old, being healthy as determined by a medical evaluation, and having been born at full term or after a gestation period above 28 weeks with a medically stable condition.

  2. Step 2

    First vaccination

    The participant will receive the first dose of the pneumococcal conjugate vaccine (PCV) through an intramuscular injection. This vaccine is designed to help protect against infections caused by pneumococcal bacteria.

  3. Step 3

    Monitoring after first vaccination

    After the first vaccination, the participant will be monitored for any immediate adverse events. This includes checking for any reactions at the injection site or any systemic reactions for up to 7 days after the injection.

  4. Step 4

    Subsequent vaccinations

    The participant will receive additional doses of the vaccine at specified intervals. The exact schedule will be provided by the study team. Each dose will be administered via intramuscular injection.

  5. Step 5

    Monitoring after each vaccination

    Following each vaccination, the participant will be observed for any immediate adverse events. Monitoring will continue for 7 days to check for any injection site or systemic reactions. Any unsolicited reactions will be recorded for 30 days after each injection.

  6. Step 6

    Final assessment

    At the end of the study period, a final assessment will be conducted to evaluate the participant's antibody response to the vaccine. This will involve measuring the levels of specific antibodies in the blood.

  7. Step 7

    Long-term follow-up

    The participant will be monitored for any serious adverse events or adverse events of special interest for up to 6 months after the last vaccine injection.

Who can join the trial?

4 criteria

  • Aged between 42 to 112 days on the day of joining the study.
  • Must be healthy, as determined by a medical check-up, which includes reviewing medical history and a physical examination.
  • Born at full term of pregnancy, which means 37 weeks or more, with a birth weight of at least 2.5 kg (about 5.5 pounds).
  • Or, born after a pregnancy period of more than 28 weeks but less than 37 weeks, with a birth weight of at least 1.5 kg (about 3.3 pounds), and in both cases, must be medically stable as assessed by the doctor.

Who cannot join the trial?

9 criteria

  • Patients who have received any other **pneumococcal vaccine** before the study cannot participate. A pneumococcal vaccine is a shot that helps protect against infections caused by the bacteria called pneumococcus.
  • Patients with a known allergy to any component of the study vaccine cannot participate. An allergy is when your body reacts badly to something that is usually harmless.
  • Patients with a history of severe allergic reactions, such as **anaphylaxis**, cannot participate. Anaphylaxis is a serious and life-threatening allergic reaction that happens quickly and needs immediate medical attention.
  • Patients with a known or suspected problem with their immune system cannot participate. The immune system is the body's defense against infections and illnesses.
  • Patients who have received blood products or immunoglobulins within the last 3 months cannot participate. Blood products and immunoglobulins are treatments that can affect the immune system.
  • Patients with a serious chronic illness that could interfere with the study cannot participate. A chronic illness is a long-lasting health condition that may not go away.
  • Patients who are currently participating in another clinical trial cannot participate. A clinical trial is a research study to test new treatments or procedures.
  • Patients who have received any other vaccine within 14 days before the study vaccine cannot participate. Vaccines are shots that help protect against diseases.
  • Patients with a fever or acute illness at the time of vaccination cannot participate. A fever is a higher-than-normal body temperature, and an acute illness is a sudden and severe sickness.
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Investigated drugs

  • PCV21

    is a 21-valent pneumococcal conjugate vaccine. This vaccine is designed to protect against 21 different types of the bacteria that can cause pneumococcal disease. Pneumococcal disease can lead to serious infections like pneumonia, meningitis, and bloodstream infections. The vaccine works by helping the body’s immune system recognize and fight these bacteria, reducing the risk of getting sick from them. In this trial, PCV21 is being tested to see how well it works in producing an immune response in healthy infants and toddlers.

  • 15vPCV

    is a 15-valent pneumococcal conjugate vaccine. Similar to PCV21, this vaccine is designed to protect against 15 different types of the bacteria that cause pneumococcal disease. It helps the immune system to recognize and combat these bacteria, aiming to prevent serious infections. In the trial, 15vPCV is used as a comparison to evaluate the effectiveness of the new PCV21 vaccine in generating an immune response in young children.

What is already known about the treatment

PCV21 – PCV21 is a vaccine administered through an injection to help protect against infections caused by pneumococcal bacteria, particularly in healthy infants and toddlers. It is currently being studied in clinical trials to assess its safety and effectiveness compared to an existing vaccine, 15vPCV. The main purpose of PCV21 is to stimulate the body's immune system to produce antibodies, specifically immunoglobulin type G (IgG), which can recognize and fight off the bacteria. This vaccine is classified as a pneumococcal conjugate vaccine and is designed to provide immunity against 21 different strains of the bacteria, including six unique strains not covered by the 15vPCV.

Investigated diseases

Pneumococcal Disease – Pneumococcal disease is caused by the bacterium Streptococcus pneumoniae, which can lead to infections in different parts of the body. It often begins with symptoms similar to a cold, such as a runny nose, cough, and fever. As it progresses, it can cause more severe conditions like pneumonia, meningitis, or bloodstream infections. The bacteria can spread from person to person through respiratory droplets. Infections can occur in the lungs, brain, or blood, leading to inflammation and other complications. The severity of the disease can vary depending on the site of infection and the individual's immune response.
Trial detailsLast updated 7 Oct 2026
Age0-17PhasePhase IIITrial ID2023-507600-32-00Protocol codePSK04Estimated enrolment1 113 patientsSponsorSanofi Vaccines US Inc.

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