TWiV reviews findings that increased fitness of the Omicron variant is due to immune evasion, not an increase in intrinsic transmissibility, and determination of infectious viral load in patients infected with wild type, Delta and Omicron viruses reveals lack of correlation with RNA loads determined by RT-PCR, similar levels of shedding among Delta and Omicron, and greatly reduced shedding in vaccinated people.

In COVID-19 clinical update #97, Daniel Griffin covers immunity after infection recognized by CDC, outcomes before and after Omicron, infectious viral load in Delta vs Omicron, PCR vs rapid antigen tests, booster interval shortened to 5 months, risk factors for severe outcomes in vaccinated, cross-reactive memory T cells, vaccine effectiveness vs MIS-C, and Rivaroxiban for thromboprophylaxis.