Fig. 5: Impact of pre-existing bRSV Ab on ChAd155-RSV vaccine efficacy.

In Study 2, calves (n = 9 biologically independent animals, see Table 1) with (Ab+) or without (Ab−) pre-existing antibodies derived from bovine RSV Ab+ or Ab− colostrum, received two doses (2D) of ChAd155-RSV or placebo, and were challenged after a short (4 weeks) duration of immunity (DOI). On day post-challenge (dpc) 12/13, animals were subjected to necropsy. The placebo-S group indicates the control group, which included 9 calves through dpc 7, decreasing to 8 calves on dpc 8, and then to 6 calves on dpc 9 to 11 (as the other calves were pre-terminated due to reaching humane endpoints). Analyzed were general illness scores (a), rectal temperatures (b), upper respiratory tract disease (URTD) scores, (c), respiratory rates (d), consolidated lung areas (CLAs; e), lung pathological changes at termination time point (f), and nasopharyngeal and lung viral loads (g, h, respectively; see Supplemental Table S1 for explanation on clinical scores). Differences between vaccine groups and the respective control groups were determined by two-sided ANOVA (with treatment as fixed effect and the appropriate variance assumption) performed either on the calculated areas under the curve (a–d) or on the single-timepoint data (e, f), or by ANOVA mixed models for repeated measurements (g, h). Means (a–f) or geometric means (g, h) with 95% confidence intervals (error bars; a–h) for each group are color-coded according to the keys in each graph. Open symbols in e, f indicate animals that were pre-terminated on dpc 7/8. Statistically significant differences are presented with asterisks color-matched with the vaccine group indicated in the key above the figure (*P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001). Source data and statistical analyses with exact P values are provided as a Source data and Supplementary Data 1 and 2, respectively.