Awareness of SARS-CoV-2 Omicron Variant Infection Among Adults With Recent COVID-19 Seropositivity

Abstract

ImportanceSome individuals who were infected by the SARS-CoV-2 Omicron variant may have been completely unaware of their infectious status while the virus was actively transmissible.ObjectiveTo examine awareness of infectious status among individuals during the recent Omicron variant surge in a diverse and populous urban region of Los Angeles County.Design, Setting, and ParticipantsThis cohort study analyzed the records of adult employees and patients of an academic medical center who were enrolled in a longitudinal COVID-19 serological study in Los Angeles County, California. These participants had 2 or more serial anti-nucleocapsid IgG (IgG-N) antibody measurements at least 1 month apart, with the first occurring 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 the present study sample.ExposuresRecent Omicron variant infection as evidenced by SARS-CoV-2 seroconversion.Main Outcomes and MeasuresAwareness of recent SARS-CoV-2 infection was ascertained from review of self-reported health updates, medical records, and COVID-19 testing data.ResultsOf the 210 participants (median [range] age, 51 (23-84) years; 136 women [65%]) with serological evidence of recent Omicron variant infection, 44% (92) demonstrated awareness of any recent Omicron variant infection and 56% (118) reported being unaware of their infectious status. Among those who were unaware, 10% (12 of 118) reported having had any symptoms, which they attributed to a common cold or other non–SARS-CoV-2 infection. In multivariable analyses that accounted for demographic and clinical characteristics, 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).Conclusions and RelevanceResults of this study suggest that more than half of adults with recent Omicron variant infection were unaware of their infectious status and that awareness was higher among health care employees than nonemployees, yet still low overall. Unawareness may be a highly prevalent factor associated with rapid person-to-person transmission within communities.

What measures should be considered in this 2022-2023 winter season

“…Why is it difficult to reach the threshold of traditional herd immunity despite such a high vaccination rate and many natural infections? Contrary to our expectations, immune evasion by the mutant forms of the virus is taking place, and according to a cohort study, 56% of patients infected during the spread of the Omicron variant had asymptomatic cases [ 3 ], making it difficult to block transmission. Since COVID-19 does not elicit systemic immunity like measles or smallpox, vaccination or natural infection does not maintain the effect of preventing infection for a long time, and resistance against intervention measures such as vaccination and mask-wearing is also believed to contribute to ongoing spread [ 4 ].…”

Serial cross-sectional estimation of vaccine-and infection-induced SARS-CoV-2 seroprevalence in British Columbia, Canada

“…[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] The extent to which such exposure history should guide recommendations regarding booster doses depends on several factors, recognizing that a large proportion may not even be aware of their previous infection status. 48 Moreover, the antigenic relatedness and immunological interactions between previously infecting viruses, the original monovalent vaccines, more recently updated bivalent vaccine strains, and currently circulating or emerging variants are complex and dynamic. Overall, our agerelated findings to date are consistent with children being the least vaccinated and most infected subgroup, whereas older adults are the most vaccinated and least infected.…”

Serial cross-sectional estimation of vaccine and infection-induced SARS-CoV-2 sero-prevalence in children and adults, British Columbia, Canada: March 2020 to August 2022

“…Among elderly adults who contribute the greatest number of severe outcomes, more than half remain reliant on vaccine-induced immunity for their protection as we enter the fall of 2022. The extent to which prior vaccine/infection history should help guide booster-dose recommendations overall depends upon a number of factors, not the least of which because a large proportion may not be aware of their infection status [46].…”