Immunogenicity of Simulated PCECV Postexposure Booster Doses 1, 3, and 5 Years after 2-Dose and 3-Dose Primary Rabies Vaccination in Schoolchildren.

Objectives. To assess the immunogenicity of intradermal (ID) booster doses of Purified Chick Embryo Cell rabies vaccine (PCECV, Rabipur) administered to Thai schoolchildren one, three and five years after a primary ID pre-exposure (PrEP) vaccination series. Methods. In this follow-up study of a randomized, open-label, phase II clinical trial, two simulated post-exposure booster doses of PCECV were administered on days 0 and 3 intradermally to 703 healthy schoolchildren, one, three or five years after primary vaccination with either two or three ID doses of 0.1 mL PCECV. Blood was drawn immediately before and 7, 14 and 365 days after the first booster dose to determine rabies virus neutralizing antibody (RVNA) concentrations. Results. An anamnestic response of approximately 30-fold increase in RVNA concentrations was demonstrated within 14 days after booster. All children (100%) developed adequate RVNA concentrations above 0.5 IU/mL. No vaccine related serious adverse events were seen in any of the vaccinees. Conclusion. ID rabies PrEP with PCECV is safe and immunogenic in schoolchildren and the anamnestic response to a two booster dose vaccination series was found to be adequate one, three, and five years after a two- or three-dose primary PrEP vaccination series.

Pre-exposure rabies vaccination using purified chick embryo cell rabies vaccine intradermally is immunogenic and safe.

OBJECTIVE: To demonstrate the safety and immunogenicity of intradermal rabies pre-exposure prophylaxis with purified chick embryo cell vaccine (PCECV) in schoolchildren age 5 to 8 years in Thailand. STUDY DESIGN: In a randomized, open-label, phase II clinical trial, 2 or 3 intradermal doses of 0.1 mL PCECV (Rabipur) were administered to 703 schoolchildren on days 0 and 28 or on days 0, 7, and 28. In 206 children, 2 simulated post-exposure booster doses were given 1 year after the primary vaccination series. Rabies virus- neutralizing antibody (RVNA) titers were determined by the rapid fluorescent focus inhibition test. RESULTS: In school-age children in Thailand, a pre-exposure immunization regimen of 3 intradermal doses of PCECV produced adequate immune responses. After primary vaccination, all subjects developed RVNA titers > or =0.5 IU/mL and demonstrated a rapid increase in RVNA titer after 2 simulated post-exposure booster immunizations 1 year after the primary vaccination series. No serious adverse drug reactions occurred. CONCLUSIONS: Rabies pre-exposure immunization with PCECV is safe and immunogenic, and its implementation could save the lives of many children in rabies-endemic areas.