A study today in Clinical Infectious Diseases conducted across 12 tertiary care pediatric hospitals in Canada and the United States shows that asymptomatic children with COVID-19, especially preschoolers, contribute significantly to household transmission.
The researchers discovered that 10.6% of exposed household contacts developed symptomatic illness within 14 days of exposure to asymptomatic test-positive children, a rate higher than expected.
"We determined that the risk of developing symptomatic illness within 14 days was 5 times greater among household contacts of asymptomatic SARS-CoV-2–positive children," the authors wrote.
They also found that 6 of 77 asymptomatic SARS-CoV-2–infected children during a 3-month follow-up developed long COVID, or 7.8% of them.
The finding is noteworthy, as likely more than 30% of all COVID-19 infections are asymptomatic, and asymptomatic infections are presumed to be benign—especially those in children.
Younger children in close contact with caregivers
The study was conducted from January 2021 to April 2022 and included 111 test-positive and 256 SARS-CoV-2 test-negative asymptomatic children. During a 14-day follow-up period, household contacts were tested for clinical (symptomatic) COVID-19, excluding households with co-primary cases among adults.
The clinical secondary attack rate (SAR) for asymptomatic positive children was 10.6% (95% confidence interval [CI], 6.5% to 16.1%). In households with test-negative asymptomatic children, the SAR was 2.0% (95% CI, 1.0% to 3.3%).
"The combined SAR among household contacts of SARS-CoV-2–positive pediatric index cases was higher if the index child was younger than 5 years, or 5 to younger than 13 years, compared to 13 to younger than 18 years of age," the authors noted.
The relative risk of SAR among index patients younger than 5 years was 11.1 (95% CI, 2.6 to 47.8), and for kids 5 to 13 years it was 8.0 (95% CI, 1.9 to 34.5). Younger children may be linked to higher SARs because of prolonged duration of viral shedding in the very young, which previous studies have demonstrated. Younger children are also in closer physical contact with their caregivers.
Among the group of children who developed long COVID, all remained asymptomatic during the 14 days following acute infection. During the 90-day follow-up, 5 of the 6 children had persistent symptoms and 1 child had newly diagnosed symptoms.
The fact that approximately 1 in 13 asymptomatically infected children developed PCC [post-COVID condition, or long COVID] is concerning and requires further investigation.
"The fact that approximately 1 in 13 asymptomatically infected children developed PCC [post-COVID condition, or long COVID] is concerning and requires further investigation," the authors concluded.
