Boostability after single-visit pre-exposure prophylaxis with rabies vaccine: a randomised controlled non-inferiority trial

Background: After rabies pre-exposure prophylaxis (PrEP) vaccination, scarcely available rabies immunoglobulins are not required for post-exposure prophylaxis (PEP). However, PrEP is not sufficiently accessible as it is cost-intensive and time-intensive. This study investigates whether rabies PrEP schedules can be shortened to one visit, removing some of these barriers. Methods: In a block-randomised (2:2:2:1) controlled, multicentre non-inferiority trial, healthy adult travellers (aged 18-50 years and >50 years) were randomly assigned to (A) single-visit intramuscular (1 center dot 0 mL); (B) single-visit intradermal (0 center dot 2 mL); (C) standard two-visit intramuscular (1 center dot 0 mL; day 0 and 7) PrEP; or (D) no rabies vaccination. 6 months later, participants received simulated intramuscular rabies PEP (1 center dot 0 mL; day 0 and 3). Rabies virus neutralising antibody (RVNA) concentrations were measured repeatedly. The primary outcome was the fold increase in geometric mean RVNA concentrations between day 0 and 7 after simulated PEP for all participants. The two main comparisons of this primary outcome are between the standard two-visit schedule and the one-visit intramuscular schedule, and between the standard two-visit schedule and the one-visit intradermal schedule. The non-inferiority margin was 0 center dot 67. This study is registered with EudraCT, 2017-000089-31. Findings: Between May 16, 2018, and March 26, 2020, 288 healthy adult travellers were randomly assigned and 214 participants were evaluated for the primary outcome. Single-visit intramuscular rabies PrEP induced an anamnestic antibody response non-inferior compared with the two-visit intramuscular schedule; single-visit intradermal PrEP did not. The fold increases in the single-visit intramuscular and the single-visit intradermal schedule were 2 center dot 32 (95% CI [1 center dot 43-3 center dot 77]) and 1 center dot 11 (0 center dot 66-1 center dot 87) times as high as the fold increase in the standard schedule, respectively. No vaccine-related serious adverse events were observed. Adverse events related to vaccination were mostly mild. Interpretation: Single intramuscular rabies vaccination can effectively prime travellers (aged 18-50 years), and potentially other populations, and could replace current standard two-visit rabies vaccination as PrEP. Copyright (c) 2023 Elsevier Ltd. All rights reserved