Many mutations in the gene that codes for the spike protein allowed the virus to more effectively infect lung cells by interacting with both the ACE2 receptor & the TMPRSS2 protease

T cell-based immunity gained against other COVID-19 variants did not provide any protection against the Omicron variant

T and B cell-based immunity gained against other COVID-19 variants did not provide any protection against the Omicron variant

Many mutations in the gene that codes for the spike protein allowed the virus to more effectively infect lung cells by interacting with the ACE2 receptor but NOT the TMPRSS2 protease