Clinical Characteristics and Outcomes Among Adults Hospitalized with Laboratory-Confirmed SARS-CoV-2 Infection During Periods of B.1.617.2 (Delta) and B.1.1.529 (Omicron) Variant Predominance — One Hospital, California, July 15–September 23, 2021, and December 21, 2021–January 27, 2022

Clinical Characteristics of COVID-19 Patients Infected by the Omicron Variant of SARS-CoV-2

“…Early studies reported by South African researchers, where the omicron variant was first discovered after nearly half population had been vaccinated and over half population had been exposed to SARS-CoV-2, suggested much attenuated pathogenicity with plummeted severity and mortality during the wide spreading of the omicron variant ( 10 , 11 , 18 ). Similar findings were also reported from other countries, including the United States, France, and South Korea ( 19 – 21 ), where vaccination coverage and population infection were both substantially high. Thereby, questions remain whether this reduced pathogenicity is due to the weakened intrinsic viremia or the strengthened acquired immunity by previous infection or/and sufficient vaccination, or both.…”

First-generation oral antivirals against SARS-CoV-2

“…The effectiveness of molnupiravir and nirmatrelvir/ritonavir should be viewed in light of the circulating SARS-CoV-2 variant, as the efficacy endpoint – COVID-19-related hospitalization – may be lower with a viral strain that is responsible for less hospitalization in immune populations (e.g., the Omicron variant as opposed to Delta [ 13 ]). The population investigated in clinical trials consisted of nonvaccinated individuals, but vaccination (and boosting) is highly recommended especially in individuals with risk factors for severe COVID-19.…”

Assessing vaccine effectiveness against severe COVID-19 disease caused by omicron variant. Report from a meeting of the World Health Organization

“…In a California hospital, 19.8% of admissions with omicron infection were deemed be not likely due to Covid-19; the median age of these admissions was 38 years old compared to 67 years old for those admitted likely due to Covid-19. [34] In one large medical center in the Netherlands, medical records review of all admissions with omicron infection during a two month period revealed that 45% were admitted for primary Covid-19 disease, 21% due to omicron infection contributing to an underlying illness, 31% due to incidental omicron infection, and 3% with an indeterminant role of omicron infection. [35]…”