key: cord-0786098-he0r4x36 authors: N, Kojima; A, Roshani; JD, Klausner title: Comparing COVID-19 PCR positivity duration for Omicron vs earlier variants date: 2022-05-21 journal: J Clin Virol Plus DOI: 10.1016/j.jcvp.2022.100085 sha: 6f8bc048126566bb4e15f939c5ca23509ae6f3bf doc_id: 786098 cord_uid: he0r4x36 There have been reports that the Omicron variant of SARS-CoV-2 is milder and may resolve more quickly than earlier variants of SARS-CoV-2, like the Delta variant. Due to a dearth of studies on duration of PCR positivity for the Omicron variant, we studied this question in a cohort of routinely tested employees that work in a large laboratory. We found that there is no difference in duration of PCR positivity among those infected with the Omicron variant of SARS-CoV-2 versus earlier variants of SARS-CoV-2. That suggests in a clinical study that the increased infectiousness of Omicron might likely be due to factors related to viral and host cell interactions, rather than viral load or duration of infectivity, which has been suggested in immune escape studies. There have been reports that the Omicron variant of SARS-CoV-2 is milder and may resolve more quickly than earlier variants of SARS-CoV-2, like the Delta variant. Due to a dearth of studies on duration of PCR positivity for the Omicron variant, we studied this question in a cohort of routinely tested employees that work in a large laboratory. We found that there is no difference in duration of PCR positivity among those infected with the Omicron variant of SARS-CoV-2 versus earlier variants of SARS-CoV-2. That suggests in a clinical study that the increased infectiousness of Omicron might likely be due to factors related to viral and host cell interactions, rather than viral load or duration of infectivity, which has been suggested in immune escape studies. The Omicron variant of SARS-CoV-2 can partially evade the humoral immune system and may have a shorter incubation period than ancestral stains (Jansen et al., 2021) . Most of the viral studies of SARS-CoV-2 infection that defined duration of infectiousness were conducted prior to en masse vaccinations and the emergence of new SARS-CoV-2 variants (Jefferson et al., 2021) . We aimed to assess if the duration of nasal PCR positivity was different for the Omicron variant of SARS-CoV-2 versus earlier variants. In March 2020, Curative, a COVID-19 testing company, began routinely screening its workforce with SARS-CoV-2 polymerase chain reaction (PCR)-based test, which was Food and Drug Administration-authorized SARS-CoV-2 (Kojima et al., 2020) . The workforce has been undergoing daily screening. In Fall 2021, the workforce was mandated to be vaccinated for COVID-19. The first case of the Omicron variant of SARS-CoV-2 in the United States was detected on 1 December 2021 and quickly became the prevalent strain of SARS-CoV-2 (Baker et al., 2021) . We aimed to assess the duration of PCR positivity before and after 1 December 2021 among infected employees, when the Omicron variant of SARS-CoV-2 became the dominant strain (Baker et al., 2021) . Infection was defined as at least 2 positive sequential nasal PCR tests. Clearance was defined as at least 2 negative sequential PCR tests. All employee samples were sent for sequencing. Analyses were performed on SQL (IBM, Armonk, NY). The study of de-identified electronic medical record data was determined by the Advarra institutional review board (Pro00054560) to be exempt from review. In the cohort, demographic characteristics were similar between groups. All employees were vaccinated (Table) . We identified 770 infections. There were 36 infections that occurred before 1 December 2021 (pre-Omicron period). Those were PCR positive for an average of 12.9 days (Standard deviation [SD]: 6.8). There were 734 infections that Omicron variants of SARS-CoV-2 were similar (Puhach et al., 2022) . PCR positivity generally lasts longer than the period an individual is infectious (Jefferson et al., 2021) . Infectiousness is predicted by an individual's viral load, duration of infection, and viral characteristics, like a virus' ability to bind to and enter a host cell (Cao et al., 2021 , Jansen et al., 2021 , Puhach et al., 2022 . Given our findings and those of Puhach et al., the increased infectiousness of Omicron might likely be due to factors related to viral and host cell interactions, rather than viral load or duration of infectivity. NK is a consultant for Curative. AR are employed by Curative. JDK is an independent consultant and serves as the Medical Director of Curative. None Omicron escapes the majority of existing SARS-CoV-2 neutralizing antibodies Investigation of a SARS-CoV-2 B.1.1.529 (Omicron) Variant Cluster -Nebraska Viral Cultures for Coronavirus Disease 2019 Infectivity Assessment: A Systematic Review Self-Collected Oral Fluid and Nasal Swab Specimens Demonstrate Comparable Sensitivity to Clinician-Collected Nasopharyngeal Swab Specimens for the Detection of SARS-CoV-2 Infectious viral load in unvaccinated and vaccinated patients infected with SARS-CoV-2 WT, Delta and Omicron SARS-CoV-2 B.1.1.529 (Omicron) Variant -United States Demographics and duration of PCR positivity for people among a cohort of employees routinely tested for SARS-CoV-2. Value Variable Before Dec 1 (N=36) On or after Dec 1 (N=734) Duration of PCR positivity None