An interventional study of Skin punch biopsy and Blood samples in Yellow Fever (Healthy Volunteers) and Biopsy/Methods, sponsored by Institute of Tropical Medicine, Belgium. Recruiting at 1 site in Belgium. Open to participants aged 18 Years to 50 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-08-13.
Sponsored by Institute of Tropical Medicine, Belgium · Not applicable, Interventional, and Other
In The main GeKoSkimm trial (= A randomized controlled trial to compare the immunogenicity and skin imprinting of intradermal, subcutaneous and intramuscular yellow fever vaccination) the investigators try to understand whether the route of injection (in the muscle, under the skin, or in the skin) when giving the yellow fever vaccine affects the strength of the body's immune response to yellow fever. More in particular the investigators want to know how well the immune responses are retained in the skin, as this is the place where the virus enters the body after a mosquito bite. This will be important for vaccines against infections transmitted via bites of mosquitoes and ticks, such as yellow fever virus. Because this is the first attempt on human samples and only skin samples after vaccination with yellow fever vaccine are available, the investigators want to assess the baseline or background immune response in 'unvaccinated' skin. Therefore, 40 volunteers will be recruited that have not been previously vaccinated against yellow fever and will not receive a yellow fever vaccine during this study. The participant will be requested to provide two skin samples from the upper arm and a blood sample to confirm their vaccination status regarded to yellow fever.
Since baseline punch biopsies were not preferred nor incorporated in the GeKoSkimm trial (= A randomized controlled trial to compare the immunogenicity and skin imprinting of intradermal, subcutaneous and intramuscular yellow fever vaccination) due to ethical and logistical reasons, studying tissue-resident memory T (TRM) cells in a group of healthy unvaccinated participants is necessary to assess natural baseline levels of TRM cells in the skin before vaccination. The presence TRM cells in healthy and unvaccinated individuals provides a fundamental understanding of normal immune function and biological variability. This baseline data is essential for interpreting responses to vaccination in the GeKoSkimm trial and detecting any deviations or abnormalities that may arise and assess the baseline or background immune response in 'unvaccinated' skin. Therefore, 40 volunteers will be recruited that have not been previously vaccinated against yellow fever and will not receive a yellow fever vaccine during this study. The study consists of two study visits with 14 days (+/- 10 days) between each visit. Blood sampling of 15 mL is performed on the first visit (1X 10 mL Li-Hep + 5 mL SST) to confirm the vaccination status against yellow fever virus (YFV). Participants who turn out positive on the YFV virus neutralization test will be retrospectively excluded from analyses, and replaced with new participants. Skin biopsy sampling (2X 4 mm punch biopsy) in the upper arm is performed only on the second visit, with additional microsampling (microbiopsy and wound blood sampling). The microbiopsy will be taken from 20 participants, followed by two skin punch biopsies from the upper arm from all participants. Subsequently, a blood swab will be collected from the wound blood from all participants.
52 studies on the registry are indexed under Yellow Fever; 10 are open to participants now.
This study's planned enrollment of 40 is below the median of 112 across 43 interventional studies indexed under Yellow Fever.
Browse Yellow Fever studies →Institute of Tropical Medicine, Belgium is the lead sponsor of 104 studies on the registry; 21 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Platelets
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Biopsy and archival tissue
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Healthy participants that have not been vaccinated against yellow fever virus
Procedure: Skin punch biopsy · Procedure: Blood samples
2 x 4mm skin punch biopsies in the upper arm will be taken from each participant at visit 2 with additional microsampling (microbiopsy and wound blood sampling)
Blood sampling of 15 mL (10mL Lithium-Heparine + 5 mL SST) is performed on Visit 1 to confirm their vaccination status regarded to yellow fever
Estimate the baseline number and proportion of skin-resident memory T cells against YFV (YFV-TRM) in the skin of unvaccinated and healthy volunteers against YFV
The number and proportion of YFV-specific T cells within the skin-resident lymphocyte parent population at visit 2, measured by flow cytometry.
Time frame: Day 14 (Visit 2)
Estimate the baseline number and proportion of circulating effector- (YFV-TEM) and central-memory T cells against YFV (YFV-TCM) in the blood of unvaccinated and healthy volunteers against YFV
The number and proportion of circulating YFV-specific TCM and TEM cells within the CD3+ lymphocyte parent population at visit 1
Time frame: Day 0 (Visit 1)
Estimate the baseline cytokine and chemokine concentrations in capillary blood, and microbiopsies of unvaccinated and healthy volunteers against YFV
The number of cytokine and chemokine concentrations (ng/ul) in capillary blood, and microbiopsies at visit 2
Time frame: Day 14 (Visit 2)
Estimate the baseline YFV-specific IgG/IgM levels in capillary blood of unvaccinated and healthy volunteers
IgG/IgM levels (mean fluorescence intensity) in capillary blood at visit 2
Time frame: Day 14 (Visit 2)
Describe the spatially-resolved position of TRM cells in the skin of unvaccinated and healthy volunteers against YFV
Spatially-resolved YFV-specific TCR clonotypes in the skin at visit 2
Time frame: D14 (Visit 2)
Determine the baseline TCR diversity index in the skin of unvaccinated healthy volunteers against YFV
TCR diversity index in the skin at visit 2
Time frame: Day 14 (Visit 2)
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