The academic literature suggests kids with COVID-19 are more likely to be asymptomatic than adults and less likely to suffer severe cases, but can pass the virus to others. Denise-Marie Ordway outlines five studies that may help to shed light on policymakers’ decisions on letting kids return to school.
During the first half of 2020, schools across the U.S. closed to prevent the spread of the new coronavirus. In recent weeks, government officials in many parts of the country have either reopened schools for the fall semester or are debating the possibility, even as epidemiologists and other researchers work to understand the role children play in transmission of COVID-19.
To date, children account for a small fraction of reported COVID-19 cases in the U.S. — 9.3% in states that report their cases by age, according to an Aug. 20 report from the American Academy of Pediatrics and the Children’s Hospital Association. But parents, teachers and others worry that reopening school campuses and resuming in-person classes will lead to an increase in coronavirus infections.
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“There is an urgent need for further investigation of the role children have in the chain of transmission,” write Alyson Kelvin and Scott Halperin, faculty in Dalhousie University’s Department of Pediatrics, in The Lancet Infectious Diseases.
The academic literature suggests kids with COVID-19 are more likely to be asymptomatic than adults and less likely to suffer severe cases, but can pass the virus to others.
In recent weeks, as schools have reopened in some states, new COVID-19 cases have emerged. In Mississippi, 22 schools reported 34 cases of coronavirus among students and employees, according to the Clarion Ledger. Meanwhile, a private school in Memphis canceled in-person classes and postponed athletics after receiving notice that 12 people tested positive for COVID-19 — nine volleyball players, one soccer player, one football player and one faculty member, the Commercial Appeal reported.
Scholars note that it’s still unclear which children should be targeted for testing and treatment, considering some don’t show symptoms of infection such as a fever and sore throat.
As of Aug. 31, about 6 million people in the U.S. had tested positive for COVID-19 and about 200,000 had died, data from the U.S. Centers for Disease Control and Prevention show. The CDC’s COVID Data Tracker and Johns Hopkins University’s Coronavirus Resource Center provide the latest tallies.
A new paper from Jonas F. Ludvigsson, a professor in the Department of Medical Epidemiology and Biostatistics at the Karolinska Institutet in Sweden, offers new insights about children and COVID-19. He examined research published or released through May 2020 on the transmission of diseases by children — a total of more than 700 scientific papers, scientific letters and texts — and drew two conclusions: Opening schools likely won’t affect COVID‐19 mortality rates in older people and children are unlikely to be the main drivers of the coronavirus pandemic.
“I think that children are at a low risk of getting very sick themselves,” Ludvigsson, who is also a senior physician in the Department of Pediatrics at Örebro University Hospital, told Journalist’s Resource in an email interview last week.
“So far, we have no deaths from COVID-19 in children aged 1-16 years (kindergarten/elementary school in Sweden), despite keeping kindergartens and schools open throughout the pandemic.”
Another new paper, based on a small sample of children in China, raises new questions about the likelihood children show symptoms when infected with the coronavirus, also referred to as SARS-CoV-2 in the scientific literature. Almost a third of those studied who tested positive for COVID-19 were asymptomatic.
Dennis Chao, a senior research scientist at the Institute for Disease Modeling in Washington, pointed out that kids who return to schools could transmit the virus to teachers, students and others on campus as well as people in their own households. But it’s difficult to know the source of an infection and to study COVID-19 in children if many are asymptomatic, he wrote in an e-mail to JR.
Chao noted that research on the role children have played in transmitting other respiratory viruses — the H1N1 influenza virus in 2009 in particular — is relevant to the current situation.
“Even though influenza does not behave exactly the same as SARS-CoV-2, it could still be the baseline of how we think about controlling the spread of respiratory pathogens,” he told JR. “And modelling groups can start with well-documented influenza models and re-parameterise them to reflect what we know about coronavirus.”
Below, we’ve highlighted and summarised five peer-reviewed studies to aid policymakers in their discussion of this issue, including two studies by Ludvigsson and Chao. We also included studies that focus on the H1N1 pandemic of 2009 and the influenza pandemic of 1918.
1. Clinical and Epidemiological Features of 36 Children with Coronavirus Disease 2019 (COVID-19) in Zhejiang, China: An Observational Cohort Study
Haiyan Qiu, et al. The Lancet Infectious Diseases, June 2020.
In this small study of 36 children with COVID-19, researchers learned that almost a third were asymptomatic and nearly two-thirds lacked fevers.
Between Jan 17, 2020 to March 1, 2020, researchers identified 36 patients aged 1 to 16 years who had tested positive for COVID-19 in Zhejiang province, China. They learned that the most common features of COVID-19 in the hospitalised children were fever, dry cough and pneumonia and that “the presentation of COVID-19 in paediatric patients is much milder than in adults.”
The average hospital stay for the 36 kids was 14 days. Ten children were asymptomatic, which is problematic, the researchers write.
“Although all paediatric patients in our cohort had mild or moderate type of COVID-19, the large proportion of asymptomatic children indicates the difficulty in identifying paediatric patients who do not have clear epidemiological information, leading to a dangerous situation in community-acquired infections,” they write.
2. Children Are Unlikely to be the Main Drivers of the COVID‐19 Pandemic — A Systematic Review
Jonas F. Ludvigsson. Acta Paediatrica, May 2020.
This new paper from Ludvigsson reviews research on COVID-19 transmission among children and from children to adults up through May 11, 2020. The author’s main findings: Opening schools likely won’t affect COVID‐19 mortality rates in older people and children are unlikely to be the main drivers of the pandemic.
“Real-world evidence points towards a limited spread of COVID-19 between children and from children,” he writes.
Ludvigsson studied more than 700 scientific papers, scientific letters and texts to better understand disease transmission by children, including their role in spreading COVID-19. He writes that research on viral loads among children – the amount of the virus that exists in an infected child’s blood – is scarce but indicates children tend to have lower levels than adults. This could be because children often have fewer symptoms, which should decrease the risk of transmission from a child, he writes.
The author notes he did not find any studies that investigate whether washing hands reduces the transmission of COVID-19 from children. He also writes that earlier research on the transmission of respiratory diseases suggests children mostly interact with other children rather than older people while they’re at school, an indication that opening schools might benefit older people.
“More time spent in kindergartens and schools may, therefore, decrease their exposure to older people, such as grandparents, who are more likely to die from COVID-19,” Ludvigsson explains.
3. Age-Related Differences in Nasopharyngeal Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Levels in Patients With Mild to Moderate Coronavirus Disease 2019 (COVID-19)
Taylor Heald-Sargent, et al. JAMA Pediatrics, July 2020.
This small study of 145 patients suggests young children with mild to moderate COVID-19 have larger amounts of SARS-CoV-2 viral RNA in their nasopharynx than do older children and adults. SARS-CoV-2 is the virus that causes COVID-19. The nasopharynx is the upper part of the throat located behind the nose.
Between March 23 and April 27, 2020, the authors analysed nasopharyngeal swabs collected from adults and children at various testing sites in the Chicago area. The researchers divided patients into three groups for analysis: 46 children younger than 5 years old, 51 children aged 5 to 17 years and 48 adults aged 18 to 65 years.
The researchers chose to exclude patients with severe infections who required supplemental oxygen support because they all tended to have high levels of SARS-CoV-2 in their upper respiratory tract.
Among patients with mild to moderate infections, children under age 5 had much higher levels of viral nucleic acid in their upper respiratory tract than did adults and older kids. That, the researchers write, indicates an approximately “10-fold to 100-fold greater amount of SARS-CoV-2.”
The study finds that “young children can potentially be important drivers of SARS-CoV-2 spread in the general population,” write the authors, led by Taylor Heald-Sargent, a paediatric infectious diseases specialist at Ann & Robert H. Lurie Children’s Hospital of Chicago and an assistant professor of paediatrics at Northwestern University Feinberg School of Medicine.
“Behavioural habits of young children and close quarters in school and day care settings raise concern for SARS-CoV-2 amplification in this population as public health restrictions are eased,” Heald-Sargent and her colleagues explain.
4. Inferring the Causes of the Three Waves of the 1918 Influenza Pandemic in England and Wales
Daihai He, et al. Proceedings of the Royal Society B, September 2013.
How did school openings and closings affect the spread of influenza during the 1918 pandemic in England and Wales? Scholars find that while school closures played an important role in controlling infection, people’s behavioural responses — for example, social distancing — had the greatest influence.
A group of researchers led by Daihai He, an associate professor of applied mathematics at Hong Kong Polytechnic University, looked at how three factors affected transmission of the deadly influenza in 1918: school openings and closings, air temperature changes and changes in human behaviour in response to the pandemic.
To compare the impact of the three factors, researchers created mathematical models based on a variety of data, including reported weekly influenza deaths during the pandemic in 334 administrative units of England and Wales and information about school terms in the United Kingdom during that time from historical documents.
He and his colleagues write that based on school calendar patterns, they assumed schools closed at three points between June 1918 and June 1919. They shuttered during harvesting season, which ran from June 23, 1918 to October 15, 1918, and then for two weeks around Christmas and New Year’s Day and a week around Easter.
Their findings suggest that the influenza transmission rate fell by an estimated 40% during school vacations and that a 10-degree change in temperature reduced the transmission rate by 43%. But behavioural changes — the steps people took to reduce their risk of catching the virus after learning others had died from it — were most important in determining the course of the pandemic, the authors explain.
“We conclude that behavioural changes, temperature trends and school closure all contributed to the observed three-wave mortality patterns in the UK during the 1918 influenza pandemic, and that behavioural changes had the largest effect,” they write.
5. School Opening Dates Predict Pandemic Influenza A(H1N1) Outbreaks in the United States
Dennis L. Chao, M., Elizabeth Halloran and Ira M. Longini Jr. The Journal of Infectious Diseases, 2010.
This study looks at the role school openings played in a surge of H1N1 infections in the U.S. in late 2009. The research team, led by Chao, finds that “detectable widespread transmission of pandemic H1N1 appears to occur 2 weeks after the opening of schools in a state.”
The researchers analysed data on influenza activity before and after public schools opened for the fall semester that year. They gathered information on opening dates in 19 states and the District of Columbia from their respective departments of education. For the other 29 states in the continental U.S., researchers obtained opening dates from 25 randomly sampled school districts in each state.
Chao and his colleagues discovered a link between elevated levels of H1N1 in a state and the median school opening date for the state. They did not, however, attempt to determine why the link exists.
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