Safety and immunogenicity of a new chromatographically purified rabies vaccine in comparison to the human diploid cell vaccine.

Background: Although human diploid cell vaccine (HDCV) has been available for over two decades and has a proven record of efficacy, it is very expensive to produce and can only be made in small quantities.

Methods: In this trial, we compared the safety and immunogenicity of a new, chromatographically purified rabies vaccine (CPRV) with those of HDCV. One hundred and thirty-five healthy veterinary students were randomized in a 2:1 ratio between CPRV and HDCV respectively. Each student subsequently received an intramuscular injection of 0.5 mL of CPRV or 1mL of HDCV on days 0, 7, and 28, according to the standard preexposure regimen. Local safety data were collected for 7 days following each dose and systemic safety data for 42 days following the first dose. Vaccine administration and safety evaluation were performed by different site personnel. Sera for immunogenicity analysis were collected on days 0 (prevaccination), 28 and 42.

Results: All subjects achieved an antirabies antibody titer greater than or equal to the World Health Organization (WHO) accepted threshold level of seroconversion of 0.5 IU/mL after only two of three doses of vaccine in both groups. The geometric mean titers (IU/mL) in the CPRV and HDCV groups respectively were 6.54 (range 0.50 to 64.80) and 10.22 (range 0.70 to 51.40) on day 28, and 40.51 (range 5.40 to 278.00) and 37.71 (range 5.40 to 278.00) on day 42. The percentage of subjects experiencing local reactions within 3 days after any dose ranged from 65.2% to 80.9% in the CPRV group and from 77.3% to 84.4% in the HDCV group. The local reaction reported by the greatest percentage of subjects after each dose was pain/tenderness at the injection site, and most reactions were mild. Most of the reported local reactions resolved within 0 to 3 days postvaccination. Systemic reactions decreased from 76.4% after dose 1 to 36.0% after dose 3 in the CPRV group, and similarly from 55.6% to 31.8% in the HDCV group. For all postdose periods, the systemic reaction reported by the highest percentage of subjects was myalgia. No subjects experienced an immediate local or systemic reaction.

Conclusions: In healthy adults, vaccination with CPRV using a preexposure schedule resulted in a safety and immunogenicity profile similar to that of HDCV.