A Phase 3 interventional study of Booster vaccination in Rabies (Healthy Volunteers), sponsored by Institute of Tropical Medicine, Belgium. Not yet recruiting at 6 sites in Belgium. Open to participants aged 18 Years to 60 Years. Per ClinicalTrials.gov, last updated 2026-03-06.
Sponsored by Institute of Tropical Medicine, Belgium · Phase 3, Interventional, and Prevention
A multicentre, open label trial in healthy volunteers to assess the boostability of three different rabies pre-exposure prophylaxis regimens (2 x 1IM regimen, 2 x 2 ID regimen, 1 x 2 ID regimen) when administering a single-dose, intramuscular vaccination as simulated post-exposure prophylaxis at least five years following priming.
This multicentre clinical trial will include 561 participants, allocated evenly across 3 groups (187 per group). Participants are assigned to one of three groups according to their prior PrEP regimen, provided their last dose was given at least 5 years prior to enrollment.
All subjects will receive 1 x 1,0 mL IM injection of purified chick-embryo cell-culture rabies vaccine as sPEP (booster) at least five years after primary vaccination (PrEP).
Neutralizing antibody titers against rabies virus will be measured using the Rapid Fluorescent Focus Inhibition Test (RFFIT) on Day 0 (before administration of sPEP) and on Days 7 and 14 after sPEP vaccination.
A titre of ≥ 0.5 IU/mL is defined as adequate (WHO standard).
114 studies on the registry are indexed under Rabies; 15 are open to participants now.
This study's planned enrollment of 561 is above the median of 201 across 104 interventional studies indexed under Rabies.
Browse Rabies studies →Institute of Tropical Medicine, Belgium is the lead sponsor of 104 studies on the registry; 21 are open to participants now.
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Exclusion Criteria:
Subjects, who received immunomodulating therapy within the last 3 months (12 weeks).
Note: See Section 6.3 for detailed guidance on immunomodulating therapies.
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.
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.
Vaccines made with a weakened form of the germ, such as measles–mumps–rubella (MMR), chickenpox and yellow fever. They can be risky when the immune system is weakened. Flu injections are not live; the nasal flu spray is.
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.
Live vaccines
Vaccines made with a weakened form of the germ, such as measles–mumps–rubella (MMR), chickenpox and yellow fever. They can be risky when the immune system is weakened. Flu injections are not live; the nasal flu spray is.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Healthy volunteers that received Pre-Exposure Prohphylaxis (PrEP) (a rabies vaccination) at least 5 years ago through 1 x 1,0 mL IM injection (Day 0 and Day 7), with a 7-day interval between visits (interval of 5 to 56 days is allowed).
Biological: Booster vaccination
Received PrEP vaccination (Pre-Exposure prophylaxis usinga rabies vaccine) at least 5 years ago through 2 x 0,1 mL ID injections (Day 0 and Day 7) with a 7-day interval between visits (interval of 5 to 56 days is allowed).
Biological: Booster vaccination
received PrEP (Pre-Exposure prophylaxis using a rabies vaccine) at least 5 years ago through 2 x 0,1 mL ID injections on Day 0
Biological: Booster vaccination
To investigate whether the boostability of a (A) two-visit IM, (B) two-visit ID and (C) one-visit ID pre-exposure vaccination regimen is non-inferior to a theoretical 99% boostability by administering a single-dose IM booster to simulate exposure to rabies at least 5 years after the pre-exposure regimens regimen.
Primary: boostability
To investigate whether the boostability of a (A) two-visit IM, (B) two-visit ID and (C) one-visit ID Pre-exposure Prophylaxis (PrEP) regimen is non-inferior to a theoretical 99% boostability when a single-dose IM simulated Post Exposure Prophylaxis (sPEP) is administered at least 5 years after the PrEP regimen. Primary Endpoint: Proportion of participants that have an adequate immune response (Rapid Fluorescent Focus Inhibition Test (RFFIT) level, WHO standard) on Day 7 after the booster.
Time frame: 13 months - from First Patient In (FPI) to Last Patient Out (LPO)
RFFIT levels ≥ 0.5 IU/mL Day 14
To estimate per arm the proportion of participant with adequate immune response on Day 14 after the booster. RFFIT levels ≥ 0.5 IU/mL is the WHO standard for adequate immune response.
Time frame: 14 days following booster vaccination
FFIT levels ≥ 0.5 IU/mL on the day of the booster (Day 0).
To estimate per arm the proportion of participant with RFFIT levels ≥ 0.5 IU/mL on the day of the booster (Day 0). RFFIT levels ≥ 0.5 IU/mL is the WHO standard for adequate immune response.
Time frame: Day 0 - on day of booster vaccination
RFFIT levels ≥ 3.0 IU/mL on Day 7 after the booster
To estimate per arm the proportion of participant with RFFIT levels ≥ 3.0 IU/mL on Day 7 after the booster. A titre ≥ 3.0 IU/ml is considered to be a proxy for good/robust protection.
Time frame: Day 7 - following booster vaccination
RFFIT levels ≥ 3.0 IU/mL on Day 14 after the booster.
To estimate per arm the proportion of participants with RFFIT levels ≥ 3.0 IU/mL on Day 14 after the booster. A titre ≥ 3.0 IU/ml is considered to be a proxy for good/robust protection.
Time frame: Day 14 after the booster vaccination
RFFIT levels ≥ 10 IU/mL on Day 7 after the booster.
To estimate per arm the proportion of participants with RFFIT levels ≥ 10 IU/mL on Day 7 after the booster. A titre ≥ 10 IU/ml is considered to be a proxy for long-lasting immunity.
Time frame: Day 14 following the booster vaccination
RFFIT levels ≥ 10 IU/mL on Day 14 after the booster.
To estimate per arm the proportion of participants with RFFIT levels ≥ 10 IU/mL on Day 14 after the booster. A titre ≥ 10 IU/ml is considered to be a proxy for long-lasting immunity.
Time frame: Day 14 following the booster vaccination.
Safety objectives
Safety objectives 1. To estimate the proportion of solicited AEs (local reactions and general symptoms) occurring within 7 days after the sPEP vaccination session. 2. To estimate the proportion of unsolicited AEs occurring within 7 days after the sPEP vaccination session. 3. To estimate the proportion of Severe Adverse Events (SAE) occurring throughout the study period after sPEP vaccination session.
Time frame: 1. & 2. Day 7 following the booster vaccination. 3. 13 months - entire study duration FPI to LPO
Plan to share: No
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This study is not yet recruiting, as verified in Mar 2026. You cannot join it, but the record below documents what was studied.
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