The COVID-19 pandemic has been accompanied by SARS-CoV-2 evolution and
emergence of viral variants that have far exceeded initial expectations. Five major variants of …

The Omicron variant was first detected in October 2021, which evolved from the original
SARS‐CoV‐2 strain and was found to possess many mutations. Immune evasion was one of …

Objectives To characterize the clinical severity of covid-19 associated with the alpha, delta,
and omicron SARS-CoV-2 variants among adults admitted to hospital and to compare the …

Trends in Disease Severity and Health Care Utilization During the Early Omicron Variant Period
Compared with Previous SARS-CoV-2 High Transmission Periods — United States, December …

Objective To evaluate the impact of vaccine scale-up on population level covid-19 mortality
and incidence in the United States. Design Observational study. Setting US county level …

Background Information regarding the protection conferred by vaccination and previous
infection against infection with the B. 1.1. 529 (omicron) variant of severe acute respiratory …

Background This phase 2b part of a randomized phase 2/3 study assessed the efficacy and
safety of ensitrelvir for mild-to-moderate coronavirus disease 2019 (COVID-19) during the …

Rising breakthrough infections of severe acute respiratory syndrome coronavirus 2 (SARS-
CoV-2) in previously immunized individuals have raised concerns for the need for a booster …

COVID-19 vaccine effectiveness decreased with waning of vaccine-derived immunity and
emerging Omicron sublineages. An updated (bivalent) booster dose enhances protection …

Background We estimated the prevalence of long COVID and impact on daily living among a
representative sample of adults in the United States. Methods We conducted a population …