Safety and immunogenicity of a new purified vero cell rabies vaccine (PVRV) administered by intramuscular and intradermal routes in healthy volunteers.

Background: Rabies is 100% fatal but preventable with modern vaccines and immunoglobulins. There is a huge demand for rabies vaccines in developing countries of Asia and Africa. We have developed a new purified vero cell rabies vaccine (PVRV) and evaluated its safety and immunogenicity in healthy volunteers by intramuscular (IM) and intradermal (ID) routes of vaccination.

Methodology: Sixty adults aged between 18 and 50 years were recruited in this actively controlled Phase I clinical study and were randomized to receive three 1 ml or 0.1 ml doses of new PVRV intramuscularly or intradermally on days 0, 7 and 21. The control group received commercially available PVRV (Verorab) by intramuscular route. Adverse events (AEs) were recorded with diary cards till day 28 post-vaccination. Immunogenicity was assessed on day 0, 7, 21 and 42 by rapid fluorescence focus inhibition test (RFFIT).

Results: In all, 116 solicited local and systemic events were reported across the three groups. Most were mild and resolved without sequelae. Also the few unsolicited events, deemed unrelated to the study vaccines, caused no problems. No significant changes in the routine laboratory parameters were found. Two doses of a vaccine elicited protective titres (≥ 0.5 IU/ml) in all subjects, the GMTs varying between 0.57 and 0.69 IU/ml on day 7, 3.07 and 3.97 IU/ml on day 21, and 6.12 and 8.52 IU/ml on day 42 post-vaccination.

Conclusions: PVRV was well tolerated and showed good immunogenicity regardless of whether administered intramuscularly or, using a tenth of that volume, intradermally. Further studies with this new vaccine are warranted.