ACE2 and infection: The spread of the virus in the lungs depends to greater extent on the cell fusion protein; therefore, Omicron may be less likely than other variants to cause severe lung disease.30 Additionally, Syrian hamsters and human angiotensin-converting enzyme 2-expressing mice have been found to have milder lung disease with the Omicron infection.31,32 A number of general population studies have also shown that Omicron appears to lead to milder cases in the population.1,2,3,4