ABSTRACT
Background: Estimates of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence in young children and risk factors for seropositivity are scarce. Using data from a prospective cohort study of households during the pre-coronavirus disease 2019 (COVID-19) vaccine period, we estimated SARS-CoV-2 seroprevalence by age and evaluated risk factors for SARS-CoV-2 seropositivity. Methods: The SARS-CoV-2 Epidemiology and Response in Children (SEARCh) study enrolled 175 Maryland households (690 participants) with ≥1 child aged 0-4 years during November 2020-March 2021; individuals vaccinated against COVID-19 were ineligible. At enrollment, participants completed questionnaires about sociodemographic and health status and work, school, and daycare attendance. Participants were tested for SARS-CoV-2 antibodies in sera. Logistic regression models with generalized estimating equations (GEE) to account for correlation within households assessed predictors of individual- and household-level SARS-CoV-2 seropositivity. Results: Of 681 (98.7%) participants with enrollment serology results, 55 (8.1%; 95% confidence interval [CI], 6.3%-10.4%) participants from 21 (12.0%) households were seropositive for SARS-CoV-2. Among seropositive participants, fewer children than adults reported being tested for SARS-CoV-2 infection before enrollment (odds ratio [OR] = 0.23; 95% CI, .06-.73). Seropositivity was similar by age (GEE OR vs 0-4 years: 1.19 for 5-17 years, 1.36 for adults; P = .16) and was significantly higher among adults working outside the home (GEE adjusted OR = 2.2; 95% CI, 1.1-4.4) but not among children attending daycare or school. Conclusions: Before study enrollment, children and adults in this cohort had similar rates of SARS-CoV-2 infection as measured by serology. An adult household member working outside the home increased a household's odds of SARS-CoV-2 infection, whereas a child attending daycare or school in person did not.
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. 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] log10 copies/mL vs 2.8 [1.8-4.4] log10 copies/mL) or by age group (median [IQR] for ages 0-4 years, 2.7 [2.4-4.4] log10 copies/mL; ages 5-17 years: 2.4 [1.1-4.0] log10 copies/mL; ages 18-74 years: 2.9 [1.9-4.6] log10 copies/mL). The number of symptoms was significantly correlated with viral load among adults (R = 0.69; P < .001) but not children (ages 0-4 years: R = 0.02; P = .91; ages 5-17 years: R = 0.18; P = .58). The highest detected viral load was greater among those with Delta variant infections (median [IQR], 4.4 [3.9-5.1] log10 copies/mL) than those with infections from variants not of interest or concern (median [IQR], 1.9 [1.1-3.6] log10 copies/mL; P = .009) or those with Alpha variant infections (median [IQR], 2.6 [2.3-3.4] log10 copies/mL; P = .006). Conclusions and Relevance: In this study, SARS-CoV-2 infections were frequently asymptomatic among children aged 0 to 4 years; the presence and number of symptoms did not correlate with viral load. These findings suggest that symptom screening may be insufficient to prevent outbreaks involving young children.