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.

• 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).

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.