Fig. 1: Immunogenicity and protective efficacy of first-generation Spike vaccine against prototype SARS-CoV-2 and VOCs Alpha and Beta.
A Vaccination scheme with prototypic YF17D-based vaccine candidate YF-S0 (S0). Syrian hamsters (n = 32 vaccinated and n = 18 sham vaccinated) were immunized twice intraperitoneally with 104 PFU of S0 on day 0 and 7 and inoculated intranasally on day 21 with 103 median tissue-culture infectious dose (TCID50) of either prototype SARS-CoV-2 (gray circles, n = 10 YF-S0 and n = 6 sham), VOC Alpha (green triangles, n = 10 YF-S0 and n = 6 sham), or VOC Beta (blue squares, n = 12 YF-S0 and n = 6 sham). B nAb titres against prototypic spike (D614G) pseudotyped virus on day 21 after vaccination, 30/32 indicates the seroconversion rates. Red datapoint indicates the NIBSC 20/130 human reference sample included as benchmark. C, D Viral loads in hamster lungs 4 days after infection quantified by quantitative RT-PCR (C) and virus titration (D). E correlates of protection against prototype SARS-CoV-2, VOC Alpha, and VOC Beta (analysis per group as in D. Logistic regression model to calculate nAb titres correlating with 50 and 90% probability for protection. Protected was defined by a viral load <102 TCID50/ml lung tissue and infected by a viral load >102 TCID50/ml lung tissue (van der Lubben et al., 2021). Shaded areas indicate 95% CI. LLOQ is lower limit of quantification. Bar graphs denote median ± IQR. Differences between groups were analyzed using nonparametric Kruskal–Wallis test uncorrected for ties.
