Clinical Trial Summary
A rabies virus neutralizing antibody (RVNA) concentration ≥ 0.5 IU/ml at 14 days after
immunization is considered a proxy for protection in vaccine efficacy studies. Abridged and
dose-sparing vaccination regimens increase accessibility and reduce both direct and indirect
costs, especially in resource-constrained countries where RABV prevalence is highest. Several
efficacy studies evaluated safety and immunogenicity of abridged regimens in healthy adult
volunteers using either four-site intradermal (ID) or intramuscular (IM) regimens, showing
them to be safe and immunogenic.
Researchers at the Institut Pasteur du Cambodge (IPC) have previously conducted a
retrospective study on clinical outcome at ≥6 months in 3318 Cambodians who received
intradermal Vero cell vaccine post-exposure prophylaxis after a bite by a rabid or
sick-looking but untested dog in 2003-2014. Here, the investigators could show that there was
no significant difference in survival among patients who received 3 versus 4 sessions of the
Thai Red Cross (TRC) ID regimen. In a separate study, investigators measured antibody
responses in order to evaluate the immunogenicity of the TRC regiment after 3 sessions versus
4 sessions. The investigators did not observe an increase in rabies virus seroneutralization
titers 14 days after the fourth immunization compared to 14 days after the third
immunization. These results contributed to changes endorsed by the WHO in its April 2018
guidelines. The "Institut Pasteur du Cambodge (IPC) regimen" of three PEP sessions of
two-site ID 0.1 mL vaccine doses each at days 0, 3 and 7 is the first one-week PEP regimen to
be recommended.
In the current research project, the aim is to compare further different PEP vaccination
strategies in a real life setting of individuals attending the rabies vaccination center at
Institut Pasteur du Cambodge (IPC) in Phom Penh, Cambodia. The antibody kinetics and cellular
immune responses in patients following either the one-week, 2-site ID regimen (IPC regimen)
or the two-week IM regimen (4-dose regimen) as well as the participants' survival for both
protocols after 6 months are evaluated.