Fig. 5. IBIS vaccination prevents Delta and Omicron variants infection and transmission.

a–c Mouse infection. Six to ten week‑old male K18‑hACE2 transgenic mice were either mock‑vaccinated or vaccinated with 2 doses of IBIS vaccine (1×10⁶ PFU/dose) as described in Fig. 3a. At 14 days post second-dose of vaccination, the mice were infected intranasally with either SARS‑CoV‑2 Delta variant (2×10³ PFU) (a) or Omicron‑BA.1 variant (1×10⁴ PFU) (b). Lungs of infected mice were harvested at day 2 and day 5 post‑infection to determine the lung viral load by plaque assay; n = 4 per group. Similarly, PBS‑ or IBIS‑vaccinated mice were infected with either Omicron‑BA.2, BA.4.1 or BA.5.2 variants (1×10⁴ PFU), and the lungs were harvested at day 3 post‑infection for lung viral load determination (c); n = 5 per group. d–g Hamster infection and transmission. Six to ten week‑old female hamsters were either mock‑vaccinated or vaccinated with 2 doses of IBIS vaccine (3×10⁶ PFU/dose) as described in Fig. 4a. On day ‑1, index hamsters were infected intranasally with either SARS‑CoV‑2 Delta variant (2×10³ PFU) or Omicron‑BA.1 variant (1×10⁴ PFU). On day 0, the infected index hamsters were co‑housed with mock- and IBIS‑vaccinated hamsters, and then separated at 24 h after co‑housing. Body weight of the hamsters was monitored for 5 days post‑infection/co‑housing (d, f). Lungs, nasal turbinate (NT) and trachea of the hamsters were harvested at day 2 and day 5 post‑infection/co‑housing for the determination of viral load by plaque assay (e, g). Delta infection and transmission experiment, n = 4 per group; Omicron‑BA.1 infection and transmission experiment, n = 3 per group. Horizontal dotted‑lines indicate detection limits for viral load determination by plaque assays. N.D., not detected. Source data are provided as a Source Data file.