Association Between 3 Doses of mRNA COVID-19 Vaccine and Symptomatic Infection Caused by the SARS-CoV-2 Omicron and Delta Variants

Abstract
On November 24, 2021, health authorities in South Africa reported the emergence of a new SARS-CoV-2 variant, B.1.1.529 (Omicron).1 Omicron has spread rapidly, and as of January 6, 2022, was identified in 149 countries across all 6 World Health Organization regions.2 Omicron was first detected in the US on December 1, 2021, and by January 1, 2022, was estimated to be responsible for 95% of sequenced new cases.3,4