Efficacy of one-dose intramuscular rabies vaccine as pre-exposure prophylaxis in travellers.

Abstract

Current guidelines for rabies pre-exposure prophylaxis (PrEP) recommend multiple vaccine doses. Travellers sometimes present for pre-travel consultation with insufficient time to complete standard PrEP schedules. We investigated the efficacy of one-dose intramuscular (IM) vaccine in priming the immune system (as PrEP) by measuring antibody response to simulated post-exposure prophylaxis (PEP). A quasi-experimental pre-post intervention clinical trial was conducted at a specialist travel clinic in Australia. Adults (≥18years) without a history of rabies vaccination were included. At Visit 1, seronegative status was confirmed and one dose of 0.5ml IM rabies vaccine (Verorab®) administered. At Visit 2 (≥60days after Visit 1), serology was repeated and a simulated PEP dose (0.5ml IM) given on this day and again 3days later (Visit 3). Serology was repeated at Visit 4 (7 days after Visit 2). A total of 94 antibody-negative participants were included (<50years [n = 50]; ≥50years [n = 44]). At Visit 2, 38.0 and 31.8% of participants aged <50 and ≥50years were antibody-positive (≥0.5 EU/ml). At Visit 4, all participants were antibody-positive; 82.0 and 47.7% of participants aged <50 and ≥50years had antibody levels >4 EU/ml, respectively. One-dose IM vaccine was effective as PrEP for priming the immune system in both age groups, resulting in rapid development of antibodies 7days after commencing simulated PEP. If there is insufficient time to complete a standard PrEP schedule, one-dose IM could be considered as an alternative schedule for short trips, rather than not offering travellers any doses at all.Clinical trials registration: ACTRN12619000946112.