Randomized Controlled Trial of the Immunogenicity and Safety of a Serum-Free Purified Vero Rabies Vaccine (PVRV-NG2) Using a Simulated Postexposure Zagreb Regimen With Human Rabies Immunoglobulin in Adults in Thailand.

Background: A serum-free, highly purified Vero rabies vaccine-next generation (PVRV-NG2) is under development. We conducted a phase III trial to describe the safety and immunogenicity profile of PVRV-NG2 compared with those of licensed purified Vero rabies vaccine (PVRV) in a simulated rabies postexposure prophylaxis (PEP) Zagreb regimen in Thailand.

Methods: Healthy adults aged ≥18 years (n = 201) were randomized in a 2:1 ratio to receive PVRV-NG2 or PVRV in a rabies PEP Zagreb (days 0, 7, 21 [2-1-1]) regimen, with concomitant human rabies immunoglobulin (HRIG) at day 0. Immunogenicity end points included the proportion of participants with rabies virus-neutralizing antibody (RVNA) titers ≥0.5 IU/mL at days 0, 14, and 35. Safety outcomes were also assessed.

Results: A total of 199 participants completed the study (PVRV-NG2 n = 133, PVRV n = 66). In the PVRV-NG2 group and PVRV group, respectively, 91.0% (95% CI, 84.1%-95.6%) and 94.6% (95% CI, 85.1%-98.9%) had RVNA titers ≥0.5 IU/mL at day 14, increasing to 100% (95% CI, 96.8%-100%) and 100% (95% CI, 93.5%-100%) by day 35. The vaccines had similar safety profiles, and there were no safety concerns.

Conclusions: PVRV-NG2 showed acceptable safety and immunogenicity profiles when co-administered with HRIG in a simulated PEP Zagreb regimen in healthy adults in Thailand.