Boostability Assessment of Three Rabies Pre-Exposure Regimens in Healthy Volunteers 5 Years Following Priming.

A Multicentre, Open-label Trial in Healthy Volunteers to Assess the Boostability of Three Different Rabies Pre-exposure Prophylaxis Regimens When Administering a Single-dose, Intramuscular Vaccination as Simulated Post-exposure Prophylaxis at Least Five Years Following Priming.

Status

Not yet recruiting

Phases

Phase 3

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT07455318

Acronym

BAZOOKA_221

Enrollment

561

Registered

2026-03-06

Start date

2026-05-15

Completion date

2027-06-01

Last updated

2026-03-06

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Rabies (Healthy Volunteers)

Keywords

Rabies, Vaccination regimens, rabies pre-exposure prophylaxis, boostability, prophylaxis, vaccination

Brief summary

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.

Detailed description

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. • Group 1: 21IM regimen, (N = 187): received PrEP 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). • Group 2: 2²ID regimen (N = 187): received PrEP 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). • Group 3: 1²ID regimen (N = 187): received PrEP at least 5 years ago through 2 x 0,1 mL ID injections on Day 0 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).

Interventions

BIOLOGICALBooster 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.

Study design

Allocation

NON_RANDOMIZED

Intervention model

PARALLEL

Primary purpose

PREVENTION

Masking

NONE

Eligibility

Sex/Gender

ALL

Age

18 Years to 60 Years

Healthy volunteers

Inclusion criteria

1. ≥ 18 to ≤ 60 years of age at time of inclusion 2. Willingness to provide written informed consent 3. Having received PrEP with a 21IM, 2²ID or 1²ID regimen at least 5 years before starting the study. For 21IM and 2²ID interval of 5 days to 56 days between the 2 visits is allowed.

Exclusion criteria

1. Known allergy to one of the components of the vaccine. 2. Subjects, who received immunomodulating therapy within the last 3 months (12 weeks). Note: See Section 6.3 for detailed guidance on immunomodulating therapies. 3. Planned vaccination with any inactivated vaccine within 2 weeks before or after vaccination in the study or with any live attenuated vaccine within 1 month before or after each vaccination in the study. 4. Ongoing pregnancy or active child wish at the time of booster vaccination (D0). 5. Any other PrEP rabies vaccine schedule/vaccination than mentioned in the inclusion criteria. 6. Previous rabies (s)PEP 7. Inability or unwillingness to comply with study procedures, including protocol-defined visits, assessments, or interventions.

Design outcomes

Primary

Measure	Time frame	Description
Primary: boostability	13 months - from First Patient In (FPI) to Last Patient Out (LPO)	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.

Secondary

Measure	Time frame	Description
RFFIT levels ≥ 0.5 IU/mL Day 14	14 days following booster vaccination	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.
FFIT levels ≥ 0.5 IU/mL on the day of the booster (Day 0).	Day 0 - on day of booster vaccination	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.
RFFIT levels ≥ 3.0 IU/mL on Day 7 after the booster	Day 7 - following booster vaccination	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.
RFFIT levels ≥ 3.0 IU/mL on Day 14 after the booster.	Day 14 after the booster vaccination	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.
RFFIT levels ≥ 10 IU/mL on Day 7 after the booster.	Day 14 following the booster vaccination	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.
RFFIT levels ≥ 10 IU/mL on Day 14 after the booster.	Day 14 following the booster vaccination.	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.
Safety objectives	1. & 2. Day 7 following the booster vaccination. 3. 13 months - entire study duration FPI to LPO	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.

Countries

Belgium

Contacts

CONTACTThomas Hendrickx, MsC

thendrickx@itg.be000000000000000000000000000000

CONTACTClinical Trial Unit Clinical Trial Unit Insitute of Tropical Medicine Antwerp, MsC

ctu@itg.be000000000000000000000000000000

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Mar 7, 2026