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Effect of liraglutide on immune response to pneumococcal polysaccharide vaccine in adults with diabetes

Verified siteRegistered drugNo placebo
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What is this trial about?

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

The study focuses on people with Diabetes, a condition that can make infections more likely. All participants receive a routine Pneumovax 23 injection, which protects against many types of the bacteria that cause pneumonia. The trial examines whether adding a medication called liraglutide, which belongs to a group of drugs known as GLP-1 receptor agonists, can improve the body’s immune response to this vaccine.

The purpose of the study is to determine if starting the GLP-1 therapy enhances the protective effect of the pneumococcal vaccine. Participants are given the vaccine and then either begin treatment with the study medication or continue with usual care (some may receive a placebo). Blood samples are taken a short time after vaccination and again several months later to see how well the immune system has responded, while safety is checked through routine visits and questionnaires.

In simple terms, the researchers measure the level of IgG antibodies, which are proteins that help the body recognize and fight the bacteria. They also look at markers of inflammation (signs that the body is reacting to infection) and count certain immune cells to see if the medication changes their numbers or function. Any side effects or serious health problems related to infection are recorded throughout the study.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial visit and first treatments

    On the day you join the study you will meet the study staff, sign the consent form, and have basic health measurements taken.

    You will receive a single intramuscular injection of pneumococcal vaccine (0.5 ml) to protect against many types of pneumococcus bacteria.

    You will also receive the first dose of liraglutide (1.8 mg) to be injected under the skin. this medication is a glp‑1 receptor agonist that is taken once each day.

  2. Step 2

    Daily liraglutide injections

    After the initial visit you will continue to inject liraglutide (1.8 mg) under the skin once every day for the duration of the study.

    The medication is supplied in a pre‑filled pen that you can use at home. you will be instructed on how to store the pen, how to prepare the dose, and how to dispose of the needle safely.

  3. Step 3

    One‑month follow‑up visit

    Approximately four weeks after the first visit you will return for a follow‑up appointment.

    A small blood sample will be taken to measure the early immune response to the pneumococcal vaccine and to check inflammation markers.

    You will complete a questionnaire about any symptoms or side effects that may be related to the vaccine or the medication.

  4. Step 4

    Four‑month follow‑up visit

    About sixteen weeks after the first visit (four months) you will attend the final study visit.

    Another blood sample will be collected to assess the main outcome: the increase in total pneumococcal igg antibody levels.

    Additional laboratory tests will evaluate immune cell numbers, leukocyte function, and any changes in inflammation markers.

    You will again answer questions about any adverse events that occurred during the study period.

  5. Step 5

    Study completion

    After the four‑month visit the study is considered complete for you.

    The study staff will thank you for your participation and may provide a summary of the study results when they become available.

Who can join the trial?

5 criteria

  • Have a diagnosis of type 2 diabetes (T2DM) and a medical reason to start a GLP‑1 receptor agonist medication because blood‑sugar control (measured by HbA1c) is not good enough or because of very high heart‑related risk.
  • Have a diagnosis of type 2 diabetes (T2DM) and be using a stable dose of the medication semaglutide (a GLP‑1 drug) for at least one year.
  • Be a healthy volunteer with a body‑mass index (BMI) between 18 and 25 kg/m², have no active chronic illness, and not take regular medicines except birth‑control pills or occasional pain relievers.
  • Be either male or female (any gender).
  • Be within the age range set by the study (adult participants as defined by the trial).

Who cannot join the trial?

5 criteria

  • Previous pneumococcal vaccination (a shot that protects against pneumonia) within the last five years, or any other vaccination in the last four weeks, disqualifies you.
  • Infection (any illness caused by bacteria, viruses, or other germs) that occurred in the past four weeks means you cannot take part.
  • Current pregnancy or breastfeeding (being pregnant or nursing a baby) makes you ineligible.
  • End‑stage renal disease (very severe kidney failure) is an exclusion.
  • Use of anti‑inflammatory therapy (medicines that reduce swelling or pain, such as ibuprofen) prevents participation.
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Investigated drugs

  • Pneumovax 23

    is a vaccine that protects against many different strains of the bacteria that can cause pneumonia. It is given as a one‑time injection into the muscle. The vaccine works by teaching the immune system to recognize the bacteria so it can fight off infection if the person is exposed later.

  • Victoza

    is a medication that works like a natural hormone called GLP‑1. It helps lower blood sugar in people with diabetes by increasing insulin release and decreasing the amount of sugar the liver makes. In this study, it is given as a subcutaneous injection to see if it can also improve the body’s immune response to the pneumonia vaccine.

What is already known about the treatment

  • Pneumovax 23

    This vaccine is given as a 0.5 ml injection into the muscle, using a pre‑filled syringe. It is an approved and widely used vaccine that protects against many types of pneumococcal bacteria. The vaccine works by presenting pieces of the bacterial surface to the immune system, which then learns to make protective antibodies. It belongs to the class of pneumococcal polysaccharide vaccines, a type of preventive immunization.

  • Victoza

    Victoza is a 1.8 mg solution for injection that is administered under the skin with a pre‑filled pen. It is an approved medicine for treating type 2 diabetes and is also used for weight management in some patients. The drug contains liraglutide, which copies a natural hormone called GLP‑1, helping the pancreas release more insulin after meals and reducing appetite. It is classified as a GLP‑1 receptor agonist, an incretin‑mimicking drug.

Investigated diseases

Diabetes mellitus - a condition where the body has trouble controlling blood sugar. It develops when the pancreas does not make enough insulin or the body cannot use it well. Over time, blood sugar stays higher than normal, which can affect how the body uses energy. The condition may start with mild symptoms and gradually become more noticeable. The high sugar can cause the kidneys, eyes, and nerves to work harder.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-525909-13-00Protocol codeR0132901Estimated enrolment100 patientsSponsorStichting Radboud universitair medisch centrum

sourced from the EU Clinical Trials Register and site verification

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