Fig. 1. SOmicron-6P vaccination elicits strong protection against SARS-CoV-2 Omicron in different animal models.
a Immunofluorescence analysis of the expression of Omicron S protein in HEK293T cells. b Schematic diagram of immunization and sample collection schedule in mice. Female BALB/c mice were intramuscularly (i.m.) immunized on a two-dose schedule with SWT-2P (1, 5, or 10 μg of mRNA, n = 10), SOmicron-6P (1, 5, or 10 μg of mRNA, n = 10), protein subunit vaccine using a dimeric form of the receptor-binding domain of WT SARS-CoV-2 (0.5, 2.5, or 5 μg of RBD-dimer protein, n = 6), or inactivated vaccine of WT SARS-CoV-2 (0.3 or 0.6 μg of SARS-CoV-2 virion, n = 5). c SARS-CoV-2 Omicron 50% virus-neutralization titers (VNT50) were determined by a plaque reduction neutralization test (lower limit of detection (LLOD) = 150) (n = 5–10). d Study design. Female hamsters were prime-vaccinated via the i.m. route on day 0 and boosted on day 21, with 0, 1, 10, 25, or 50 μg of SOmicron-6P (n = 6). On day 30 after the initial immunization, hamsters were intranasally challenged with 1 × 104 PFU of SARS-CoV-2 Omicron. On day 4 after infection, hamsters were euthanized for tissue collection. e VNT50 values were determined by a plaque reduction neutralization test (LLOD = 150) (n = 6). f Viral RNA load in both lungs, and nasal turbinates were determined by qRT-PCR (n = 3–4). g Viral load expressed in PFU per gram of tissue in both lungs, and nasal turbinates at 4 days postinfection (n = 3–4). h Study design. Male macaques were i.m. immunized with 20 or 100 μg SOmicron-6P (n = 3) and boosted with the same dose at a 21-day interval. i–l VNT50 against SARS-CoV-2 Omicron (i), WT (j), Beta (k), and Delta (l) that were determined by a plaque reduction neutralization test (LLOD = 150) (n = 3). Data are shown as means ± SEM. Significance was calculated using one-way ANOVA with multiple comparisons tests (n.s. not significant, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001).