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Household Transmission Dynamics of Asymptomatic SARS-CoV-2-Infected Children: A Multinational, Controlled
Anna Funk1, Todd A Florin2,3, Nathan Kuppermann4,5
1Department of Obstetrics and Gynecology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
Insights
Asymptomatic children with SARS-CoV-2 drive household transmission, with 1 in 10 contacts developing symptoms. Some infected children also experience post-COVID-19 condition (PCC), highlighting the need for further research.
Area of Science:
- Pediatric infectious diseases
- Virology
- Epidemiology
Background:
- Asymptomatic SARS-CoV-2 infection in children is common but poorly understood regarding its acute and long-term effects.
- Limited data exists on the transmission dynamics and chronic health implications of asymptomatic pediatric COVID-19 cases.
Purpose of the Study:
- To investigate the role of asymptomatic children in household transmission of SARS-CoV-2.
- To determine the incidence of symptomatic illness in household contacts exposed to asymptomatic SARS-CoV-2-infected children.
- To assess the prevalence of post-COVID-19 condition (PCC) in asymptomatic children following infection.
Main Methods:
- A controlled, case-ascertained household transmission study involving asymptomatic children under 18 years old across 12 pediatric institutions in Canada and the US.
- Recruitment of SARS-CoV-2 nucleic acid test-positive children and test-negative controls, followed by 14-day assessment of secondary attack rates (SARs) in household contacts.
- 90-day follow-up for SARS-CoV-2-positive children to evaluate for post-COVID-19 condition (PCC).
Main Results:
- The clinical secondary attack rate (SAR) in household contacts of asymptomatic SARS-CoV-2-positive children was 10.6%, compared to 2.0% for contacts of negative children (Relative Risk=5.4).
- Factors associated with increased SAR included younger age (<5 years), pre-symptomatic status, and infection during Omicron/Delta variant periods.
- Among 77 asymptomatic SARS-CoV-2-infected children, 7.8% reported post-COVID-19 condition (PCC) at 90 days.
Conclusions:
- Asymptomatic SARS-CoV-2-infected children, particularly those under 5, significantly contribute to household transmission, leading to symptomatic illness in approximately 1 in 10 contacts.
- A notable proportion of asymptomatic children infected with SARS-CoV-2 may develop post-COVID-19 condition (PCC).
Background:
Asymptomatic SARS-CoV-2 infection in children is highly prevalent but its acute and chronic implications have been minimally described.
Methods:
In this controlled case-ascertained household transmission study, we recruited asymptomatic children <18 years with SARS-CoV-2 nucleic acid testing performed at 12 tertiary care pediatric institutions in Canada and the United States. We attempted to recruit all test-positive children and 1 to 3 test-negative, site-matched controls. After 14 days' follow-up we assessed the clinical (ie, symptomatic) and combined (ie, test-positive, or symptomatic) secondary attack rates (SARs) among household contacts. Additionally, post-COVID-19 condition (PCC) was assessed in SARS-CoV-2-positive participating children after 90 days' follow-up.
Results:
A total of 111 test-positive and 256 SARS-CoV-2 test-negative asymptomatic children were enrolled between January 2021 and April 2022. After 14 days, excluding households with co-primary cases, the clinical SAR among household contacts of SARS-CoV-2-positive and -negative index children was 10.6% (19/179; 95% CI: 6.5%-16.1%) and 2.0% (13/663; 95% CI: 1.0%-3.3%), respectively (relative risk = 5.4; 95% CI: 2.7-10.7). In households with a SARS-CoV-2-positive index child, age <5 years, being pre-symptomatic (ie, developed symptoms after test), and testing positive during Omicron and Delta circulation periods (vs earlier) were associated with increased clinical and combined SARs among household contacts. Among 77 asymptomatic SARS-CoV-2-infected children with 90-day follow-up, 6 (7.8%; 95% CI: 2.9%-16.2%) reported PCC.
Conclusions:
Asymptomatic SARS-CoV-2-infected children, especially those <5 years, are important contributors to household transmission, with 1 in 10 exposed household contacts developing symptomatic illness within 14 days. Asymptomatic SARS-CoV-2-infected children may develop PCC.
