Lack of Awareness of Omicron Variant Infectious Status in More than Half of Adults Contributes to High Transmission Rates

More than half of adults with recent Omicron variant infection were unaware of their infectious status, according to a study recently published in JAMA Network Open. Although health care workers were found to have better awareness, overall awareness was found to be low.

The rapid spread of the SARS-CoV-2 Omicron variant across communities has been attributed to several factors, including limited coverage by available vaccines, changes in face mask use and socializing behaviors, and particularly great transmissibility compared to previous SARS-CoV-2 variants.

However, unknown variables exist, including the extent to which infected individuals may be unaware of their infectious status. Previous research indicates that asymptomatic or minimally symptomatic SARS-CoV-2 infections are likely triggers of outbreaks and rapid transmission.

Researchers conducted a longitudinal cohort study to examine awareness of infectious status among individuals during the recent Omicron variant surge. The study analyzed records of adult employees and patients of Cedars-Sinai Medical Center who were enrolled in a longitudinal COVID-19 serological study in a diverse and populous region in Los Angeles County, California.

Participants had 2 or more serial anti-nucleocapsid immunoglobulin G (IgG-N) antibody measurements at least 1 month apart. The first occurred after the end of a regional Delta variant surge (September 15, 2021) and a subsequent one occurring after the start of a regional Omicron variant surge (December 15, 2021).

Adults with evidence of new SARS-CoV-2 infection occurring during the Omicron variant surge period through May 4, 2022, were included in this sample. Researchers measured awareness of recent SARS-CoV-2 infection through review of self-reported health updates medical records, and COVID-19 testing data. Participants completed surveys on exposures and symptoms at baseline and time points over the course of the study.

The analysis included 210 participants with serological evidence of recent Omicron variant infection (median [range] age, 51 (23-84) years; 136 women [65%]). Of these participants, 44% (92) demonstrated awareness of any recent Omicron variant infection, whereas 56% (118) reported being unaware of their infectious status. Among those who were unaware, 10% (12) reported having had symptoms, which they had attributed to a common cold or other non-SARS-CoV-2 infection.

Analyses revealed that participants who were health care employees of the medical center were more likely than nonemployees to be aware of their recent Omicron variant infection (adjusted odds ratio, 2.46; 95% CI, 1.30-4.65).

“This finding may be explained not only by the differences in general health awareness and literacy between employees and nonemployees but also by the mandatory daily screening protocols for employees that are supported by COVID-19 sick pay policies, which were broadened at the institution during the Omicron variant surge,” the authors wrote.

Additionally, younger and male individuals were determined to be more likely to be aware of recent Omicron variant infection.

Overall, most individuals with Omicron variant infection were unaware of their COVID-19 status. The relatively high level of unawareness of Omicron variant infection was determined to depend on symptoms and variations in the use of diagnostic testing. The majority of those who were unaware were asymptomatic.

These findings suggest that lack of awareness of Omicron variant infection likely had a role in rapid transmission within communities in Los Angeles County, either due to relative absence of symptoms or lack of timely testing. The results build upon previous research suggesting that asymptomatic and undiagnosed SARS-CoV-2 infections are critical factors in transmission.

The authors suggest that serological assessments can help with understanding patterns of susceptibility to emerging SARS-CoV-2 variants. They also emphasize that the greater availability and use of rapid antigen testing could be associated with augmented awareness and reduced transmission rates.

However, they encourage further studies to more completely understand the factors associated with unawareness of infectious status, particularly those factors that could be mitigated by available interventions.

This study has some limitations. The modest sample size had limited statistical power to detect multiple factors associated with Omicron variant infection awareness.

The researchers encourage larger studies to identify additional potentially important factors. They also attributed seroconversion during the regional Omicron variant surge to the Omicron variant or its subvariants, despite being unable to confirm the actual strain of the virus through sequencing.

Finally, seroconversion events could not be uniformly verified by concurrent or contemporary PCR testing in all cases. However, the study authors assert that the serology assays used have demonstrated overall high specificity, and the analyses of awareness of infection yielded consistent results.

Reference

Young S Y, Ebinger J E, Sun N, et al. Awareness of SARS-CoV-2 Omicron variant infection among adults with recent COVID-19 seropositivity. JAMA Netw Open. 2022;5(8):e2227241. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2795246. Published August 17, 2022. Accessed August 17, 2022.