Incidence Rates, Household Infection Risk, and Clinical Characteristics of SARS-CoV-2 Infection Among Children and Adults in Utah and New York City, New York

Abstract

Importance: Data about the risk of SARS-CoV-2 infection among children compared with adults are needed to inform COVID-19 risk communication and prevention strategies, including COVID-19 vaccination policies for children.

Objective: To compare incidence rates and clinical characteristics of SARS-CoV-2 infection among adults and children and estimated household infection risks within a prospective household cohort.

Design, setting, and participants: Households with at least 1 child aged 0 to 17 years in selected counties in Utah and New York City, New York, were eligible for enrollment. From September 2020 through April 2021, participants self-collected midturbinate nasal swabs for reverse transcription-polymerase chain reaction testing for SARS-CoV-2 and responded to symptom questionnaires each week. Participants also self-collected additional respiratory specimens with onset of COVID-19-like illness. For children unable to self-collect respiratory specimens, an adult caregiver collected the specimens.

Main outcomes and measures: The primary outcome was incident cases of any SARS-CoV-2 infection, including asymptomatic and symptomatic infections. Additional measures were the asymptomatic fraction of infection calculated by dividing incidence rates of asymptomatic infection by rates of any infection, clinical characteristics of infection, and household infection risks. Primary outcomes were compared by participant age group.

Results: A total of 1236 participants in 310 households participated in surveillance, including 176 participants (14%) who were aged 0 to 4 years, 313 (25%) aged 5 to 11 years, 163 (13%) aged 12 to 17 years, and 584 (47%) 18 years or older. Overall incidence rates of SARS-CoV-2 infection were 3.8 (95% CI, 2.4-5.9) and 7.7 (95% CI, 4.1-14.5) per 1000 person-weeks among the Utah and New York City cohorts, respectively. Site-adjusted incidence rates per 1000 person-weeks were similar by age group: 6.3 (95% CI, 3.6-11.0) for children 0 to 4 years, 4.4 (95% CI, 2.5-7.5) for children 5 to 11 years, 6.0 (95% CI, 3.0-11.7) for children 12 to 17 years, and 5.1 (95% CI, 3.3-7.8) for adults (≥18 years). The asymptomatic fractions of infection by age group were 52%, 50%, 45%, and 12% among individuals aged 0 to 4 years, 5 to 11 years, 12 to 17 years, and 18 years or older, respectively. Among 40 households with 1 or more SARS-CoV-2 infections, the mean risk of SARS-CoV-2 infection among all enrolled household members was 52% (range, 11%-100%), with higher risks in New York City compared with Utah (80% [95% CI, 64%-91%] vs 44% [95% CI, 36%-53%]; P < .001).

Conclusions and relevance: In this study, children had similar incidence rates of SARS-CoV-2 infection compared with adults, but a larger proportion of infections among children were asymptomatic.

Figure 1.. Cohort Recruitment, Screening, Consent, and Surveillance Participation, Coronavirus Household Evaluation and Respiratory Testing Cohort in Utah and New York City, New York

^aSurveillance participation was defined as submitted at least 1 weekly or acute illness respiratory sample.

Figure 2.. SARS-CoV-2 Infection Incidences per 1000 Person-Weeks by Site and Age in Utah and New York City, New York, From September 2020 Through April 2021 (N = 1236)

Error bars denote 95% CIs. All incidence estimates are adjusted for household clustering using negative-binomial models with generalized estimating equations assuming independent correlation structure. Overall age-stratified incidence estimates are also adjusted for site.

Figure 3.. SARS-CoV-2 Infection Symptom Status and Symptom Frequency Among Children vs Adults (N = 84)

This figure includes 84 individuals with SARS-CoV-2 infection who had complete information about symptom status and/or specific symptoms. Questionnaires for children younger than 24 months excluded chills, muscle aches or body aches, change in taste or smell, sore throat, joint pain, nausea, abdominal pain, headache, or chest pain because these symptoms can be difficult for caregivers to identify in younger children who are nonverbal or less verbal; infections in children younger than 24 months are excluded from analyses of these symptoms in the age group 0 to 17 years. No child younger than 24 months had increased fussiness (data not shown). There were significant differences (P < .05) between children and adults in the frequency of being symptomatic, being asymptomatic, having muscle aches, having chills, having excessive fatigue, having headaches, having a cough, having a sore throat, having nasal congestion/runny nose, experiencing a change in taste or smell, having joint pain, and having eye redness.