SARS-CoV-2 Omicron Variant Has Mean Shed Duration of 5 Days

For the SARS-CoV-2 Omicron variant, the mean duration of viable virus shedding and polymerase chain reaction (PCR) positivity is 5.16 and 10.82 days, respectively, according to a study in the International Journal of Infectious Diseases.

Investigators conducted a systematic review and meta-analysis assessing the duration of viable virus shedding and PCR positivity of the SARS-CoV-2 Omicron variant in the upper respiratory tract. Toward that end, they searched the PubMed, Cochrane, and Web of Science databases for relevant articles published from November 2021 to December 2022. Outcomes of interest were conversion time to negative viral culture and conversion time to negative PCR results.

A total of 29 studies (with 230,227 patients) were included. Of the studies, 7 were conducted in the US, 11 were case series, 16 were cohort studies, 1 was a randomized controlled trial, and 1 was a nonrandomized clinical trial.

A total of 11 studies (including a total of 384 participants) reported on the duration of viable virus shedding of Omicron. The duration of pooled viable virus shedding was 5.16 days (95% CI, 4.18-6.14). The maximum number of days of viable virus shedding was 15 in the upper respiratory tract.

A total of 23 studies (involving 230,013 participants) analyzed Omicron’s duration of PCR positivity. The pooled PCR positivity duration was 10.82 days (95% CI, 10.23-11.42), with a maximum PCR positivity duration of 23 days in the upper respiratory tract.

Subgroup analysis found that the mean duration of PCR positivity was slightly higher in symptomatic patients than in asymptomatic patients in 1 study, although the difference was nonsignificant. In another study, no difference was observed between symptomatic and asymptomatic patients. In 1 study that analyzed the duration of viable virus shedding in symptomatic and asymptomatic patients, the duration was comparable between the 2 groups.

Regarding patients with different vaccination statuses, 1 study found a mean duration of viable virus shedding of 3.00 days (95% CI, 2.09-3.91) for fully vaccinated (2 doses) patients and 2.67 days (95% CI, 1.96-3.37) for booster- vaccinated (3 total doses) patients. Another study found that full or booster vaccination shortened the duration of PCR positivity (adjusted hazard ratio, 1.40; P =.001).

Among several limitations, almost all patients received various treatments, which could have modified the shedding dynamics. Also, many studies provided no information on the daily virus culture and PCR test results of patients, and few studies evaluated the duration of viable virus shedding of Omicron. Furthermore, most studies reported shedding duration with median and interquartile range values, but the meta-analysis required their conversion to mean and standard deviation values.

“Although Omicron may exhibit a long duration of PCR positivity (approximately 23 days), most studies reported no live virus isolation beyond day 10 after symptom onset,” said study authors. “Although Omicron RNA shedding from respiratory samples can be prolonged, the duration of viable virus is relatively short,” they explained, noting that these findings have implications for future pandemic and infection control strategies.

This article originally appeared on Pulmonology Advisor