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NCT Number: NCT07455318

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 (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.

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Key information

Conditions

Rabies (Healthy Volunteers) Infections Mononegavirales Infections RNA Virus Infections Rabies Rhabdoviridae Infections Virus Diseases

Age range

18 year–60 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 3

Primary location

Clinical Trial Site Insitute of Tropical Medicine, Antwerp, Belgium

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About this study

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).

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • ≥ 18 to ≤ 60 years of age at time of inclusion
  • Willingness to provide written informed consent
  • 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

  • Known allergy to one of the components of the vaccine.
  • Subjects, who received immunomodulating therapy within the last 3 months (12 weeks).

Note: See Section 6.3 for detailed guidance on immunomodulating therapies.

  • 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.
  • Ongoing pregnancy or active child wish at the time of booster vaccination (D0).
  • Any other PrEP rabies vaccine schedule/vaccination than mentioned in the inclusion criteria.
  • Previous rabies (s)PEP
  • Inability or unwillingness to comply with study procedures, including protocol-defined visits, assessments, or interventions.

Treatment and study plan

Booster vaccination

Biological

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 outcomes

  1. Primary: boostability

    Time frame: 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 outcomes

  1. RFFIT levels ≥ 0.5 IU/mL Day 14

    Time frame: 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.

  2. FFIT levels ≥ 0.5 IU/mL on the day of the booster (Day 0).

    Time frame: 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.

  3. RFFIT levels ≥ 3.0 IU/mL on Day 7 after the booster

    Time frame: 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.

  4. RFFIT levels ≥ 3.0 IU/mL on Day 14 after the booster.

    Time frame: 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.

  5. RFFIT levels ≥ 10 IU/mL on Day 7 after the booster.

    Time frame: 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.

  6. RFFIT levels ≥ 10 IU/mL on Day 14 after the booster.

    Time frame: 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.

  7. Safety objectives

    Time frame: 1. & 2. Day 7 following the booster vaccination. 3. 13 months - entire study duration FPI to LPO

    Safety objectives

    • To estimate the proportion of solicited AEs (local reactions and general symptoms) occurring within 7 days after the sPEP vaccination session.
    • To estimate the proportion of unsolicited AEs occurring within 7 days after the sPEP vaccination session.
    • To estimate the proportion of Severe Adverse Events (SAE) occurring throughout the study period after sPEP vaccination session.

Study contacts

Contact information is provided by the study sponsor or research team.

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

CONTACT

[email protected]

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Thomas Hendrickx, MsC

CONTACT

[email protected]

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Sponsors and collaborators

Lead sponsor

Institute of Tropical Medicine, Belgium

Other

Registry information

Official study title

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.

Acronym: BAZOOKA_221

Important dates

Study start
2026
Primary completion
2027
Study completion
2027
First posted
Mar 6, 2026
Registry last updated
Mar 6, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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