Comparative Long-Term Immunogenicity and Boosting of 3-Session Versus 4-Session Intradermal Rabies Post-Exposure Prophylaxis Regimens in Cambodia and Madagascar: The RESIST-3 Study

The abridged Institut Pasteur du Cambodge 3-session intradermal (ID) rabies post-exposure prophylaxis (PEP) regimen has been shown to be as safe and immunogenic as the 4-session regimen previously recommended by the World Health Organization. This regimen reduces time and cost and improves adherence and access to PEP for underserved people. In our study, we aimed to compare long-term and anamnestic immune response after a rabies vaccine booster dose in people previously vaccinated with a 3- or 4-session ID PEP.

In this prospective, multisite, comparative immunogenicity study, we measured rabies virus (RABV)-neutralizing antibody in 181 persons who had previously received 3- or 4-session ID PEP 2, 5, or 10 years earlier in Cambodia or Madagascar at day 0 and day 7 after a booster. In addition, RABV-specific T-cell response was evaluated in a subgroup of 35 Cambodian participants.

All participants had RABV-neutralizing antibody titers considered adequate (≥0.5 IU/mL) on day 7 after the booster dose. The overall geometric mean titer of rabies antibody on day 0 and day 7 did not differ significantly between the 2 groups. Furthermore, RABV-specific T-cell response was similar regardless of the ID PEP regimen initially received in a subgroup of 35 participants.

In this multisite, real-world study, we showed that the 3-session ID PEP regimen provides robust long-term immunogenicity for up to 10 years after initial PEP and ensures the induction of an adequate anamnestic response within 7 days after an additional booster in all participants.