Safety and immunogenicity of an inactivated vero cell-based rabies vaccine (Rabivax-S) in pre-exposure prophylaxis schedule in Vietnam.

Purpose: We evaluated the immunogenicity and safety of Rabivax-S (Pitman-Moore 3218 strain) by intramuscular (IM) and intradermal (ID) routes in Vietnam. Materials and Methods: We conducted an open-label, randomized, phase 4, single-center clinical trial in healthy individuals aged five to 60 years divided into two groups according to age (5-15 years old and 16-60 years old). They were randomized to receive 3 doses of Rabivax-S IM 1 mL) or Rabivax-S ID (0.1 mL) in 1:1 ratio on days 0, 7, and 21. Adverse events (AEs) were collected for 7 days after each dose and rabies-neutralizing antibody levels were measured were measured by RFFIT on days 0, 21 and 42. Results: Totally 220 participants aged 5-15 years old (117 participants) and 16-60 years old (103 participants). The seroconversion rates of antibodies among the two groups (IM and ID doses) were all 100.0% on D21 and D42/42. On D21 and D42/42, the geometric mean concentration of the two groups was much higher than the immune protection level of 0.5 IU/mL. There were no AEs or serious AEs recorded in all four visits. Unsolicited AEs were reported by 3% of participants. The most common AEs during seven days after each dose were fever, pain, and erythema. Mostly mild local and systemic AEs were reported across the two groups and all resolved without sequelae. Conclusion: The study results conclusively demonstrate that the complete regimen of both the IM and ID 3-dose series Rabivax-S was found to be clinically safe and immunogenic. After this study, Rabivax-S is now available in Vietnam and can be used for pre- and post-exposure prophylaxis. Clinical Trials Registration: ClinicalTrials.gov Identifier: NCT05937113.