Children are not only less susceptible to Covid-19, they may also play a smaller role in spreading it.
(CN) — Along with a child’s curiosity comes a seemingly inherent disregard for hygiene as they explore the world through taste and touch. Emerging research nevertheless suggests kids aren’t a main source of spreading SARS-Cov-2, the coronavirus that causes Covid-19. A paper published in the journal PLOS Computational Biology on Thursday modeling household outbreaks in Israel indicates kids are much less likely to pass on Covid-19 than adults.
Researchers at the University of Israel analyzed Covid-19 test results taken from 3,353 people in 637 households in Bnei Brak from March to May 2020 while the city was under lockdown. An Israeli city with a population of 213,046, the average household size in Bnei Brak is 5.3 and roughly 51% of residents are under the age of 20.
At the time, the district physician approved testing all members of any household where one person exhibited symptoms of Covid-19. Both PCR, or transcriptase-polymerase chain reaction tests, and serological blood tests were conducted.
Of the data collected, 65% of adults tested positive for Covid-19 and 28% of children under the age of 20.
Overall, the model suggest children under 20 years old are only 43% as susceptible to the disease as adults and 63% as likely to infect others.
“A key question is whether the above-noted difference between children and adults in rates of identified cases is the result of lower susceptibility of children to infection, or perhaps is due to the milder or no symptoms displayed by infected children, which, based on common testing policy, leads to under-detection,” the paper notes.
Scientists are still trying to understand why children put up such a strong resistance to SARS-CoV-2, the virus that causes Covid-19. Some suggest children have lower levels of ACE2 receptors which the virus uses to infect cells. Others wonder whether children are being protected from Covid-19 by the same T-cells that help them fight off the viruses that cause the common cold.
According to Johns Hopkins University, Covid-19 killed 2.3 million people worldwide and infected at least 107 million. To date the U.S. confirmed 27.3 million cases of Covid-19 and 471,000 deaths.
The American Academy of Pediatrics reports 2.93 million children have tested positive for Covid-19 in the U.S., making up about 12.9% of cases nationwide. Of these, less than 2.3% were hospitalized and fewer than 1% died.
While children under the age of 1 are at high risk of illness, a Johns Hopkins guide reiterates that children 1 to 10 are at low risk of disease and transmission. Children 10 to 18 years old are at a higher risk compared to the younger age group, but a lower risk compared to higher ages groups.
“Many people also find it difficult to put Covid-19 into perspective,” said Jonas Ludvigsson, a professor of clinical epidemiology at Karolinska Institute in Stockholm. Over the last year, Ludvigsson has treated and studied Covid-19 in children including several who suffered long-term symptoms.
Ludvigsson nevertheless noted that cancer infected children in Sweden at three times the rate of Covid-19 over the last year and that more kids died in traffic accidents than from the pandemic.
“I see children with Covid-19 in the hospital almost every week,” Ludvigsson said in an email. “While I feel sad for every child with severe Covid-19, I think it is important to keep in mind that lockdowns and school closures also have consequences for children.”
Closing schools became a widely used strategy throughout the pandemic to slow the spread of Covid-19. While some communities in the U.S. and around the world opted to reopen with dips in cases and rises in public pressure, others remain shuttered.
Research published in the journal Chaos on Tuesday concluded that while lockdowns overall reduced infection rates by 72% and the death rate by 76%, closing schools contributed very little.
By modeling social interactions and rates of infection in New York City, researchers at the University of Hong Kong found school closures may have reduced disease spread by 4%, but implementing social distancing guidelines decreased infections by 47% and cut the death rate in half.
“School only represents a small proportion of social contact,” said Qingpeng Zhang, one of the authors in a statement. “It is more likely that people get exposure to viruses in public facilities, like restaurants and shopping malls. Since we focus here on the severe infections and deceased cases, closing schools contributes little if the elderly citizens are not protected in public facilities and other places.”
While the data appears hopeful, researchers are quick to caution against moving too quickly.
“It is important that our estimates of lower susceptibility of children relative to adults not be misunderstood to imply that efforts to protect children are not crucial,” Yair Goldberg, associate professor at the Israel Institute of Technology and co-author on the study on household outbreaks in Israel, said in an email.
“As we have written, the fact that interactions among children are more intense, in particular in school contexts, could offset the effect of lower susceptibility, leading to high infection rates among children as societies re-open, in particular as children are presently not vaccinated,” Goldberg cautioned.