Assessment of Clinical and Virological Characteristics of SARS-CoV-2 Infection Among Children Aged 0 to 4 Years and Their Household Members

Abstract

IMPORTANCEFew 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 realtime 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.RESULTS Among 690 participants (355 [51.4%] female and 335 [48.6%] male), 256 individuals (37.1%) were children aged 0 to 4 years, 100 (14.5%) were children aged 5 to 17 years, and 334 (48.4%) were adults aged 18 to 74 years. A total of 15 participants (2.2%) were Asian, 24 (3.5%) were Black, 603 (87.4%) were White, 43 (6.2%) were multiracial, and 5 (0.7%) were of other races; 33 participants (4.8%) were Hispanic, and 657 (95.2%) were non-Hispanic. Overall, 54 participants (7.8%) had SARS-CoV-2 infection during the surveillance period, including 22 of 256 children (8.6%) aged 0 to 4 years, 11 of 100 children (11.0%) aged 5 to 17 years, and 21 of 334 adults (6.3%). Incidence rates per 1000 person-weeks were 2.25 (95% CI, 1.28-3.65) infections among children aged 0 to 4 years, 3.48 (95% CI, 1.59-6.61) infections among children aged 5 to 17 years, and 1.08 (95% CI, 0.52-1.98) infections among adults. Children aged 0 to 17 years with SARS-CoV-2 infection were more frequently asymptomatic (11 of 30 individuals [36.7%]) compared with adults (3 of 21 individuals [14.3%]), with children aged 0 to 4 years most frequently asymptomatic (7 of 19 individuals [36.8%]). The highest detected viral load did not differ between asymptomatic vs symptomatic individuals overall (median [IQR], 2.8 [1.5-3.3] log 10 copies/mL vs 2.8 [1.8-4.4] log 10 copies/mL) or by age group (median [IQR] for ages 0 -4 years, 2.7 [2.4-4.4] log 10 copies/mL; ages 5-17 years: 2.4 [1.1-4.0] log 10 copies/mL; ages 18-74 years: 2.9 [1.9-4.6] log 10 cop...

How Do We Stop the Spread of SARS-CoV-2 in Young Children?

“…9 In addition, vaccination against SARS-CoV-2 has been reported to prevent progression to multisystem inflammatory syndrome in children among adolescent patients during the period when Delta and Omicron variants were circulating. 10 The prospective household cohort study by Karron et al 4 found that young children are important reservoirs of SARS-CoV-2 infection and that relying on symptom-based testing may not be enough to mitigate the transmission of SARS-CoV-2 among children aged 0 to 4 years, an age group that now has safe and beneficial vaccines available for use. Vaccination against SARS-CoV-2 will likely be the best strategy to diminish the spread of virus and prevent severe disease in children.…”

“…The study by Karron et al 4 revealed the importance of SARS-CoV-2 infection in children, although several limitations of the study were noted by the authors. The first was that the study does not necessarily represent the general population; for example, 87.4% of the study population selfreported their race as White, and household members required online access to enter study data.…”

“…Elsewhere in this journal, Karron and colleagues 4 have helped to answer important questions regarding the spread of SARS-CoV-2 in the household setting. They prospectively examined the incidence and clinical features of SARS-CoV-2 household infection, with a focus on children aged 0 to 4 years.…”

Etiology and Epidemiology of Croup before and throughout the COVID-19 Pandemic, 2018–2022, South Korea

“…However, the clinical significance in children and adolescents has remained stably low compared to that in adults and elderlies [ 4 ]. In addition, asymptomatic infection is common in children [ 5 ]. The reason for this is still not clearly explained, but recent exposure to other viruses and routine vaccines—including but not limited to Bacillus Calmette–Guérin (BCG), measles-mumps-rubella (MMR), and tetanus-diphtheria-pertussis (Tdap) in children—are presumed to be associated with protective cross-reactive antibodies and T cells against SARS-CoV-2, based on a recent study [ 6 ].…”

Predictors of Severe Acute Respiratory Syndrome Coronavirus 2 Seropositivity Before Coronavirus Disease 2019 Vaccination Among Children 0–4 Years and Their Household Members in the SEARCh Study

“…Although children are susceptible to SARS-CoV-2 infection and can transmit the virus to others [ 2 ], relatively few studies have focused on disease characteristics and patterns of transmission among children aged 0–4 years. Children are more frequently asymptomatic or mildly symptomatic compared with adults [ 3 ], and some household studies have found asymptomatic transmission to be significantly lower than symptomatic transmission [ 4 , 5 ]. Because children are more likely to be asymptomatic when infected with SARS-CoV-2, they are also less likely to be tested, and their infections are less likely to be detected.…”