Impact of age and symptom development on SARS-CoV-2 transmission in households with children—Maryland, New York, and Utah, August 2020–October 2021

Background Households are common places for spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We investigated factors associated with household transmission and acquisition of SARS-CoV-2. Methods Households with children ages <18 years were enrolled into prospective, longitudinal cohorts and followed August 2020─August 2021 in Utah, September 2020─August 2021 in New York City, and November 2020─October 2021 in Maryland. Participants self-collected nasal swabs weekly and with onset of acute illness. Swabs were tested for SARS-CoV-2 using reverse-transcription polymerase chain reaction. We assessed factors associated with SARS-CoV-2 acquisition using a multi-level logistic regression adjusted for household size and clustering and SARS-CoV-2 transmission using a logistic regression adjusted for household size. Results Among 2,053 people (513 households) enrolled, 180 people (8.8%; in 76 households) tested positive for SARS-CoV-2. Compared to children <12y, odds of acquiring infection were lower for adults ≥18y (adjusted odds ratio[aOR]:0.34, 95% confidence interval[CI]:0.14–0.87); however, this may reflect vaccination status, which protected against SARS-CoV-2 acquisition (aOR:0.17, 95%CI:0.03–0.91). Odds of onward transmission was similar between symptomatic and asymptomatic primary cases (aOR:1.00, 95%CI:0.35–2.93) and did not differ by age (12–17vs. < 12y aOR:1.08, 95%CI:0.20–5.62; ≥18vs. < 12y aOR:1.70, 95%CI:0.52–5.83). Conclusions Adults had lower odds of acquiring SARS-CoV-2 compared to children, but this association might be influenced by COVID-19 vaccination, which was primarily available for adults and protective against infection. In contrast, all ages, regardless of symptoms and COVID-19 vaccination, had similar odds of transmitting SARS-CoV-2. Findings underscore the importance of SARS-CoV-2 mitigation measures for persons of all ages.