Younger children more likely to spread COVID-19, study finds

Young children may be more likely to transmit the virus that causes COVID-19 within households compared with older children, a new study has found.

Specifically, children 3 or younger were more likely to spread the virus to household members compared with those aged 14 to 17.

The study, published in JAMA, analyzed public health data from Ontario, Canada, to identify COVID clusters in which a child was the primary case within households.

This study updates experts' understanding of COVID transmission risk, experts said. Earlier in the pandemic, some scientists suggested the risk of transmission declined with age. But this assumption was likely skewed by the fact that lockdowns and social distancing meant young children had very few social encounters.

"In some ways, this is the opposite of what we had been told in the past," said Dr. Edith Bracho Sanchez, a primary care pediatrician and assistant professor of pediatrics at Columbia University Irving Medical Center. "It just shows how humble we have to be when it comes to children and this virus."

"We always knew children could get it, could transmit it, and could get sick with COVID," she added. "I think we're learning more and more just how much."

Meanwhile, babies and toddlers are probably more likely to spread disease to parents and caregivers because they are cared for directly, in close contact.

"The 0-to-3-year-old child is held differently, is cuddled," said Dr. Paul Offit, director of the Vaccine Education Center and professor of pediatrics in the Division of Infectious Diseases at Children's Hospital of Philadelphia.

The risk of death and severe illness is still much lower in younger children compared with older children and adults. This study doesn't mean that very young children are more likely to die if infected with COVID, rather they may be more likely to transmit the virus than previously thought.

The study period took place in 2020, prior to the emergence of the delta variant, so more research is needed to understand transmission risk in the context of the variant. The study also took place prior to vaccines being available, meaning all household members were unvaccinated.

Pediatricians said this study reinforces the importance of existing mitigation strategies at childcare facilities and schools, including distancing, good ventilation, frequent cleaning and masking whenever possible.

It also reinforces the importance of all eligible people over 12, especially those around young children, getting vaccinated.

"We've let our kids down," Offit said. "The moat around the fire is the parents. They can be vaccinated."