Key Points

Question Do community-acquired SARS-CoV-2 infections differ in adults and children aged 0 to 4 years with respect to incidence, symptoms, and detected viral load?

Findings In this cohort study of 690 participants from 175 households in Maryland conducted from November 2020 to October 2021, 54 incident SARS-CoV-2 infections were detected in 8.6% of children aged 0 to 4 years, 11.0% of children aged 5 to 17 years, and 6.3% of adults. Children were more frequently asymptomatic or mildly symptomatic than adults; highest detected viral loads correlated with the number of symptoms in adults but not in young children.

Meaning This study’s findings suggest that symptomatic screening for SARS-CoV-2 infection may be insufficient to control outbreaks in settings in which young children congregate.

Abstract

Importance Few studies have prospectively assessed SARS-CoV-2 community infection in children aged 0 to 4 years. Information about SARS-CoV-2 incidence and clinical and virological features in young children could help guide prevention and mitigation strategies.

Objective To assess SARS-CoV-2 incidence, clinical and virological features, and symptoms in a prospective household cohort and to compare viral load by age group, symptoms, and SARS-CoV-2 lineage in young children, older children, and adults.

Design, Setting, and Participants This prospective cohort study enrolled 690 participants from 175 Maryland households with 1 or more children aged 0 to 4 years between November 24, 2020, and October 15, 2021. For 8 months after enrollment, participants completed weekly symptom questionnaires and submitted self-collected nasal swabs for SARS-CoV-2 qualitative real-time reverse transcriptase polymerase chain reaction (RT-PCR) testing, quantitative RT-PCR testing, and viral lineage determination. For the analyses, SARS-CoV-2 Alpha and Delta lineages were considered variants of interest or concern. Sera collected at enrollment and at approximately 4 months and 8 months after enrollment were assayed for SARS-CoV-2 spike and nucleocapsid protein antibodies.

Main Outcomes and Measures Incidence, clinical and virological characteristics, and symptoms of SARS-CoV-2 infection by age group and correlations between (1) highest detected viral load and symptom frequency and (2) highest detected viral load and SARS-CoV-2 lineage.

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