Cotton rats (N = 6) were immunized twice with 25 μg mRNA/LNP vaccine or DS-Cav1 formulated with Adju-Phos®. Sera was isolated 4 weeks following the second immunization and assayed for neutralization of RSV A (Long) and RSV B (18537). a NT50 titers calculated as described above for RSV-A (Long) (white square) and RSV-B (18537) (black circle) are plotted for each group. The center bar indicates the geometric mean titers and error bars show the 95% confidence interval. The limit of detection titer of 4 is indicated by a dashed line. No difference between NT50 titers for RSV-A and RSV-B was detected for any of the groups by two-sided paired t-test. b Animals were challenged with RSV B 18537 4 weeks after the second immunization. Nose and lung tissue were collected 4 days following challenge and assayed for the presence of RSV by plaque assay. Lung titers (black circle) and nose titers (white square) are shown for each animal. Geometric mean titer with 95% CI is shown for each group. The assay limit of detection (LOD) is 100 for lung titers and 40 for nose titers; each is indicated on the graph with a dotted line. Animals with no RSV infection measured were plotted at the LOD.