<i>Notes from the Field: </i>SARS-CoV-2 Omicron Variant Infection in 10 Persons Within 90 Days of Previous SARS-CoV-2 Delta Variant Infection — Four States, October 2021–January 2022

Abstract

Vaccination protects against infection with SARS-CoV-2 (the virus that causes COVID-19) and related hospitalizations (1,2), and surviving a previous infection protects against B.1.1.7 (Alpha) and B.1.617.2 (Delta) variant reinfections (2).Since the SARS-CoV-2 B.1.1.529(Omicron) variant became predominant in the United States in late December 2021, reported reinfections have increased (3).Early reinfections (those occurring within 90 days of previous infection) are not well understood (4).Because some persons have prolonged detection of viral RNA after infection, repeat positive nucleic acid amplification test (NAAT) results within 90 days could reflect prolonged shedding from earlier infection, presenting technical challenges to documenting and characterizing early reinfections.This report describes 10 patients from four states, with whole genome sequencing (WGS)-confirmed Omicron variant infections within 90 days of a previous Delta infection.This activity was reviewed by CDC, approved by respective institutional review boards, and was conducted consistent with applicable federal law and CDC policy.