Naïve BALB/c mice were treated with PBS or immunized intranasally with 106 PFU of rPIV5-RSV-F, rPIV5-RSV-G, or RSV A2. At 4 weeks post-immunization, mice were challenged with 106 PFU of RSV A2. At 4 days post-challenge, lungs were harvested and viral load was determined by plaque assay in Vero cells. Each group consisted of 5 mice. Solid horizontal lines represent the geometric mean of each group. Statistical significance was determined by ANOVA and Tukey multiple comparison tests. *, P < 0.05. LOD, limit of detection.