KRT18 and infection: The K18-hACE2 mice vaccinated with either 3 μg or 6 μg doses of ERUCoV-VAC were fully protected after challenge, and there were no obvious weight loss changes among the two vaccinated groups, whereas mice vaccinated with PBS succumbed to infection within 6 days due to ≥25% weight loss or a poor body condition (Figure 3b,c).