Viral RNA and antibody titers in vaccinated and challenged guinea pigs. A, Quantitative reverse-transcription polymerase chain reaction analysis to detect Lassa virus (LASV) nucleoprotein (NP) RNA in guinea pig tissues at the time of euthanasia (ie, acute disease in the mock-vaccinated group and at the end of the observation period in the VRP-vaccinated groups). Averages and ranges are shown. B, Prechallenge and postchallenge immunoglobulin M (IgM) and immunoglobulin G (IgG) antibody titers against LASV as determined by enzyme-linked immunosorbent assay (ELISA). Ranges and medians are shown.