Immunogenicity and safety of an inactivated Rift Valley fever vaccine in a 19-year study

Abstract An investigational, formalin-inactivated Rift Valley fever (RVF) vaccine, known as The Salk Institute-Government Services Division (TSI-GSD) 200 vaccine, was administered to 1860 at-risk subjects (5954 doses) between 1986 and 2004 as a three-dose primary series (days 0, 7, and 28) followed by booster doses as needed for declining titers. An initial positive serological response (PRNT80 ≥ 1:40) to the primary series was observed in 90% of subjects. Estimate of the PRNT80 response half-life in initial responders to the primary series by Kaplan–Meier plot was 315 days after the primary series dose 3. Differences in a serological response were observed at 2 weeks after dose 3 of the primary series between vaccine lots and for gender (women > men); a trend was observed for age (