1. Children aged 0 to 3 years old were more likely than children aged 14 to 17 to transmit SARS-CoV-2 to other household members.
Evidence Rating Level: 2 (Good)
The impact of children on SARS-CoV-2 transmission during the COVID-19 pandemic is not entirely clear. In part, this is due to many household studies grouping younger adults and children within the same age cohort. As well, although some meta-analyses found no significant differences in household susceptibility to COVID-19 between younger and older children, there have been mixed results for household infectivity. The current cohort study based in Ontario, Canada analyzed instances where children were the index case in their household, to determine the odds of transmission to other household members. Pediatric cases were split into 4 age categories: 0-3, 4-8, 9-13, and 14-17. Secondary cases were defined as people with onset of disease between 1 and 14 days after the pediatric index case. In total, 6280 private households between June and December 2020 had a pediatric index case, with a mean (SD) age of 10.7 (5.1) years. 27.3% of these households had a secondary transmission, with pediatric index cases more often transmitting to those aged 0-20 and 30-50. Index cases were higher as age increased, with 12% of cases being in the 0-3 years group, 20% in the 4-8 years, 30% in 9-13 years, and 38% in 14-17 years. Compared to children aged 14-17 years, those aged 0-3 years had higher odds of transmission (odds ratio 1.20, 95% CI 1.01-1.45), but there was no significant difference for the 9-13 age group. The 4-8 age group had a significantly higher transmission odds after adjusting for gender, month of disease onset, family size, and testing delay (OR 1.40, 95% CI 1.18-1.67). Furthermore, every day that a test was delayed, the odds of transmission increased (compared to 0 days, ORs of 1.24 and 1.59 corresponded to 1 and 2 day delays respectively). Overall, this study showed that younger children, in particular those between the ages of 0 and 3, are more likely than older children to transmit SARS-CoV-2 to other household members, underlying the importance of implementing household infection control practices since socially isolating young children may be unfeasible.
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