One of the most contentious questions during Australia’s fight against coronavirus has been whether it is safe to send children back to school.
Chief medical officer Brendan Murphy has repeatedly advocated for a careful reopening of schools, saying he has seen no evidence nationally or internationally of large school-based outbreaks of COVID-19.
This begs the question - why has this highly-infectious virus had little effect on children around the world to date?
Why aren’t children coming down with severe cases of COVID-19?
While nobody has been able to answer this question with 100 per cent certainty, scientists believe the answer lies in how a child's immune system interacts with the infection.
Professor Kristine Macartney is a paediatric infectious disease specialist and the director of the National Centre of Immunisation Research and Surveillance.
She believes the virus has not spread out of control in schools because immune systems react differently when someone is young.
Professor Kristine Macartney is a paediatrician specialising in infectious diseases. Source: Supplied
“When you get a viral infection, it’s often an interaction between how much virus can enter your cells and how much of it is able to replicate without being controlled by the immune system, but then we see in this disease that the immune system can even get itself out of control,” Professor Macartney told SBS News.
“There’s an immune reactivity we see in some adults that leads to a condition called acute respiratory distress syndrome and another condition called a systemic inflammatory response syndrome.
“Both of these suggest to us that the immune system in adults can actually overcompensate or overreact to COVID-19, but we haven’t seen much of that at all in children.”
Professor Macartney’s team conducted a study in NSW that found .
They tracked more than 860 students and teachers who were close contacts of the cases in those 15 schools for 28 days.
Only two of those close contacts contracted the virus, and neither of them is believed to have spread it any further.
“It’s fascinating and it’s actually been a surprise to us in the paediatric community, because we’re so used to children being the super spreaders of other viruses, particularly for influenza,” Professor Macartney said.
Why aren’t those children with COVID-19 spreading it to others?
While there have been cases of children becoming seriously ill and even dying from the coronavirus overseas, Professor Macartney said these cases were the exception rather than the rule.
It appears the less severe infections among children are also linked with lower rates of transmission.
“They’re not presenting with symptoms as often, they have milder disease, and now there’s evidence they’re not transmitting as much,” Professor Macartney said.
“We think some children might be dead ends for the virus - they might catch it and not necessarily spread it to anyone else.”
While one primary school student in Professor Macartney’s study had caught the virus from a teacher, there were no instances of transmission from student to teacher.
“We think there’s very little child-to-child transmission and low likelihood of child-to-adult transmission as well,” Professor Macartney said.
“This virus appears to spread mainly between adults.”
In the Netherlands, where more than 38,800 cases of COVID-19 have been confirmed, the National Institute for Public Health and the Environment has also been studying the transmission of the virus.
Contact tracing found nobody under the age of 18 had passed it on.
“The spread of COVID-19 mainly takes place between persons of approximately the same age,” the researchers said.
“Children are less likely to be infected by adults, and when this does happen, it turns out that it is mainly in the home situation.”
The study also found there were no children under 12 who had been the first household member to become infected, and those children who did become infected consistently presented with less severe symptoms. 
A Netherlands teacher sets up her classroom tables and chairs 1.5 meters apart in preparation for schools reopening. Source: LightRocket
Should parents feel comfortable sending their kids back to school?
As each Australian state’s daily number of new infections starts to slow, governments are now setting plans in place to reopen schools.
Infectious disease epidemiologist Dr Meru Sheel said Australia’s pandemic was now at the point where the risk of spreading the virus could be more easily managed in the classroom.
, Dr Sheel said it was not quite time to let kids run wild on the playground.
“While it might be onerous and extra work for schools and teachers, it’s about weighing up the risks against the benefits of getting schools back to face-to-face learning,” Dr Sheel told SBS News.
Epidemiologist Dr Meru Sheel says the benefits of reopening schools need to be weighed against the risks. Source: ANU
“Social distancing measures still have to be strongly in place - hand hygiene, cough etiquette, if teachers or children are sick then they must stay home - but the risk will be minimal if we continue to practise these prevention measures.”
However, on the scale of those experienced in late May and early April, Dr Sheel said schools would have to reevaluate their plans.
“If we had wide-scale community transmission, it would become a different conversation,” she said.
“Then you’d want to keep everyone home again, because that’s the only way to stop transmission.”
People in Australia must stay at least 1.5 metres away from others and gatherings are limited to two people unless you are with your family or household.
If you believe you may have contracted the virus, call your doctor (don’t visit) or contact the national Coronavirus Health Information Hotline on 1800 020 080. If you are struggling to breathe or experiencing a medical emergency, call 000.
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