Children Infectious a Median of 3 Days With Omicron Variant of SARS-C0V-2

For nearly all children, five days out of school should be more than enough time after they test positive for Covid-19, according to a new study that suggests they are infectious for a median of 3 days. The new study also notes that children have a shorter duration of illness than adults — an average of 3 vs. 5 days.

LOS ANGELES – Pharmacists often are asked when children infected with the Omicron variant of SARS-CoV-2 can return to school. Parents are concerned whether the usual five-day stay-at-home requirement is adequate or too much.

A new study in JAMA Pediatrics provides an answer to the question. Researchers from the University of Southern California and Stanford University found that five days is more than sufficient because children infected with the Omicron variant remained infectious for a median time of three days after testing positive for the virus.

“We're basically saying five days is more than sufficient; public health and education leaders may consider shorter durations,” said co-author Neeraj Sood, PhD, director of the COVID-19 Initiative and a senior fellow at the USC Schaeffer Center.

“COVID-19 quarantine and self-isolation policies continue to interrupt education,” the authors write. “These policies, while typically more stringent than for routine viral illnesses, are guided by few data; the duration of SARS-CoV-2 infectivity in children is largely unknown.”

The study points out that one study determined that nasopharyngeal samples from infected children, compared with adults, were half as likely to contain culturable virus. In light of the lack of information, the researchers evaluated the duration of infectivity and its association with vaccination using live viral recovery over a 10-day window after a positive COVID-19 test result in children in Los Angeles County.

Between April and September 2022, the cohort study recruited children aged 7 to 18 years who had a positive result via polymerase chain reaction test for COVID-19. Researchers obtained pharyngeal swabs during 5 home visits over 10 days from 81 children (5 lost to follow-up), with day 0 designated as the date of a positive test result.

Of the 76 participants, 52 (68.4%) were vaccinated, 41 (55.4%) were aged between 7 and 12 years, 38 (50.0%) were male, and 38 (50.0%) were female. Results suggested a median duration of infectivity of 3 (95% CI, 3-3) days, with 14 participants (18.4%) infectious on day 5 and 3 (3.9%) on day 10.

The median duration of infectivity among vaccinated children was 3 (95% CI, 3-3) days among unvaccinated children, 3 (95% CI, 2-3) days.

“The lack of association between vaccination status and infectivity was robust to controlling for demographics,” the authors point out. “Among vaccinated children, duration of infectivity was similar for children who received a booster vs. those who did not. These results were consistent with our sensitivity analysis using date of symptom onset as origin of observation.”

School rules, however, appeared to be guided by little data, the authors suggested.

“We want to protect the other children in the school who could potentially get infected, but at the same time, we don't want to disrupt education for the child who is infected, given the amount of disruption that's already happened,” Sood said. “The duration of infectivity is an important parameter into figuring out what the optimal duration of self-isolation should be.”

The researchers said their findings are consistent with previous research on adults who contracted the Omicron variant, which showed no association between vaccination status and time of infectivity. It also indicated that adults with Omicron were infected slightly longer, with a median time of five days.

“We wanted to capture how infectivity changed over the 10-day window,” explained lead author Nikhilesh Kumar, a Doctor of Medicine student at the USC Keck School of Medicine.