Characterization of SARS-CoV-2 Omicron persistence and infectivity amongst youngsters

In a latest examine posted to the medRxiv* preprint server, researchers characterised the persistence and infectivity of extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron amongst youngsters.

Study: Persistence of SARS-CoV-2 omicron variant in children and utility of rapid antigen testing as an indicator of culturable virus. Image Credit: L Julia/Shutterstock
Examine: Persistence of SARS-CoV-2 omicron variant in children and utility of rapid antigen testing as an indicator of culturable virus. Picture Credit score: L Julia/Shutterstock


For the reason that first experiences of coronavirus illness 2019 (COVID-19), our understanding of SARS-CoV-2 transmission has developed with the emergence of newer variants. In July 2020, the USA (US) Facilities for Illness Management and Prevention (CDC) beneficial a 10-day isolation interval for SARS-CoV-2-infected people with out the necessity for an related unfavorable end result.

The Florida Division of Well being (FDOH) in September 2021 dominated that contaminated youngsters might return to varsities sooner than ten days, supplied that they take a look at unfavorable for SARS-CoV-2 and present no signs.

In January 2022, the CDC up to date the rules, lowering the isolation interval to 5 days and allowing contaminated adults/youngsters to return to workplaces/colleges if afebrile; nonetheless, masking was obligatory for 5 extra days. Moreover, in February 2022, the FDOH permitted the return of contaminated youngsters after 5 days of isolation with out taking assessments or utilizing masks.

Concerning the examine

Within the current examine, researchers characterised the prevalence and infectivity of SARS-CoV-2 Omicron amongst youngsters. These with a constructive SARS-CoV-2 end in a polymerase chain response (PCR) or fast antigen take a look at (RAT) have been recognized from the College of Florida (UF) Well being pediatric clinics or referred by college nurses at a neighborhood public college.

They enrolled children who confirmed signs for 5 days or longer with sampling between December 20, 2021, and February 21, 2022. Mother and father’ samples have been additionally collected when a number of youngsters from the identical household have been enrolled within the examine. After enrolment, nasal swab samples have been obtained from 31 youngsters (16 years or youthful) and eight from three dad and mom.

The workforce collected two specimens from every participant. One pattern was instantly examined with a BinaxNOW RAT, and the opposite was frozen till subsequent reverse-transcriptase quantitative PCR (RT-qPCR), tradition assessments, willpower of viral load, and genome sequencing.

These with a constructive take a look at end result throughout the first follow-up returned on days 7, 10, or till a unfavorable end result was recorded. Completely different cell strains have been used for viral cultures, corresponding to LLC-MK2, Vero E6, A549, and HEK293T cells. They noticed cells for a month, and the presence of the virus was verified by an RT-PCR take a look at when cytopathic results (CPE) turned evident.


Two-thirds of the youngsters have been boys, and the median age was seven. Ten had unfavorable RAT outcomes at enrolment that corresponded to their fourth day (or later) of symptom onset or after preliminary constructive end result (from UF Well being or college referrals). They noticed at the least one constructive RAT for the remaining youngsters; subsequently, 14 examined unfavorable.

Assuming that each one youngsters could be SARS-CoV-2-positive earlier than their final constructive end result, the authors calculated that greater than a 3rd of them could be SARS-CoV-2-positive on day 5, and 48% would nonetheless take a look at constructive on RAT by day 7. Subsequent, the workforce estimated the length of youngsters being constructive over time by becoming a parametric survival mannequin.

The mannequin predicted that youngsters would stay constructive for 7.74 imply days, with a ten% drop within the likelihood of being constructive by day 12. SARS-CoV-2 cultures have been carried out on 23 samples. Virus cultures have been constructive for 16 samples, and all have been RAT-positive. Seven culture-negative samples have been additionally RAT-negative. Furthermore, a big correlation was famous between RAT and tradition outcomes.

Forty samples have been RAT-positive, and all examined constructive in RT-qPCR assessments. Of the 25 RAT-negative samples, 9 have been RT-qPCR-positive; 4 of those samples have been cultured and produced unfavorable outcomes. Sequencing revealed that each one constructive samples have been of Omicron BA.1 variant. The phylogenetic analysis didn’t discover a lot variability, in keeping with the circulation of a single SARS-CoV-2 clade.


The authors reported that just about half the contaminated youngsters would have been SARS-CoV-2-positive for no less than two days had they returned to varsities based mostly on the CDC’s January 2022 pointers. Though masks would have decreased the transmission, masking observe was controversial in Florida, given the FDOH’s February 2022 suggestions.

From a public well being perspective, limiting SARS-CoV-2 transmission by contaminated youngsters in colleges is crucial. Thus, extending the five-day isolation interval earlier than returning to high school needs to be thought-about with the requirement of a unfavorable RAT end result.

*Vital discover

medRxiv publishes preliminary scientific experiences that aren’t peer-reviewed and, due to this fact, shouldn’t be considered conclusive, information scientific observe/health-related habits, or handled as established data.

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