Abstract
Objectives: Studies of household transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) focused on households with children are limited. We investigated household secondary attack rate (SAR), transmission dynamics, and contributing factors in households with children.Materials and Methods: In this prospective case-ascertained study in Los Angeles County, California, all households members were enrolled if ≥1 member tested positive for SARS-CoV-2 by polymerase chain reaction (PCR). Nasopharyngeal PCRs, serology, and symptom data were obtained over multiple visits.Results: A total of 489 individuals in 105 households were enrolled from June to December 2020. The majority (77.3%) reported a household annual income of <$50,000, and most (92.9%) were of Hispanic/Latinx ethnicity. Children <18 years old accounted for 46.9% index cases, of whom 45.3% were asymptomatic. Household index cases were predominantly children during low community transmission and adults during the high community transmission period (χ2 = 7.647, p = 0.0036. The mean household SAR was 77.0% (95% CI: 69.4–84.6%). Child and adult index cases both efficiently transmitted SARS-CoV-2 within households [81.9%, (95% CI: 72.1–91.9%) vs. 72.4% (95% CI: 59.8–85.1%), p = 0.23]. Household income and pets were significantly associated with higher SAR in the multivariable analysis of household factors (p = 0.0013 and 0.004, respectively).Conclusions: The SAR in households with children in an urban setting with a large ethnic minority population is much higher than previously described. Children play important roles as index cases. SAR was disproportionately impacted by household income. Vaccination and public health efforts need special focus on children and vulnerable communities to help mitigate SARS-CoV-2 spread.
Highlights
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has continued to spread rapidly worldwide, leading to over 4.2 million deaths globally [1]
Households in Los Angeles County, California were prospectively enrolled into the Household Exposure and Respiratory Virus Transmission and Immunity Study (HEARTS) if at least one household member tested positive for SARS-CoV-2 within 2 weeks prior to enrollment and at least two members living in the household agreed to participate
One household was excluded because all members except for the index case had documented COVID19 infection >3 months earlier
Summary
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has continued to spread rapidly worldwide, leading to over 4.2 million deaths globally [1]. Published studies show a household attack rate of 47% and a secondary attack rate (SAR) ranging from 6 to 53 percent among household contacts [5,6,7,8,9,10,11,12,13,14], with a mean SAR of 16.6% on a meta-analysis of 44 studies by Madewell et al [5]. Previous studies suggest that children under 18 years old are unlikely to be index cases and result in a lower attack rate, that secondary attack rates are higher in adults than children, and that asymptomatic index cases have a limited role in household transmission [5, 15,16,17,18]. The number of Coronavirus disease 2019 (COVID-19) cases in children, has been on the rise since summer 2020, paralleling trends among adults [19]
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