Extract from ABC News
By national medical reporter Sophie Scott and ABC specialist reporting team's Loretta Florance
Francesca Orsini was preparing to celebrate her daughter's second birthday when the family received a call from Victoria's Department of Health, telling them the toddler had tested positive for COVID-19.
Key points:
- Most children who contract coronavirus do not get seriously ill
- Researchers studied 28 Melbourne households who were infected or exposed to the virus
- They found children's innate immune systems react to the virus in a way not seen in adults
Two-year-old Camilla was the last in the family of four confirmed as having the virus but, while Francesca and her partner Alessandro Bartesaghi were struck down with headaches and fatigue, Camilla and her five-year-old sister Beatrice sailed through the illness with only minor symptoms.
"The kids, they were OK. They were jumping and running everywhere like always, so that was tough," Alessandro Bartesaghi said.
A new study from the Murdoch Children's Research Institute (MCRI) in Melbourne has found children are protected from severe COVID-19 because their innate immune system attacks the virus in a way not seen in adults.
The study, which the family took part in, involved an analysis of blood samples from 48 children and 70 adults across 28 households infected with, or exposed to, coronavirus.
Lead researcher Melanie Neeland said the findings gave experts a new understanding as to why children don't get as sick as their parents.
"We know that children are less likely to be infected with coronavirus and we know that up to one third can be asymptomatic, but what we didn't really understand is why this was the case — especially for coronavirus, which appears to be quite unique because in most other respiratory viruses, we know that children appear to be the most affected," Dr Neeland said.
Dr Neeland and her team monitored immune responses of the families during the acute phase of infection and up to two months afterwards.
"We showed an increased inflammatory response and we showed reduced proportions of infection fighting immune cells in the blood of children with COVID-19," she said.
"I think the most interesting part was that this robust, innate immune response was not observed in adults with COVID-19."
"So what it showed to us was that in children, these first responder innate immune cells were migrating to sites of infection which were clearing the virus before it really had a chance to take hold, and this was not observed in adults."
'Who's going to look after a positive kid?'
When Francesca and Alessandro took their five-year-old daughter Beatrice to get tested for COVID-19 in early July 2020, Melbourne was not yet in full lockdown.
Case numbers were going up, but face masks were not mandatory and the family had spent the day at the park with friends.
They didn't think Beatrice, who had a runny nose, actually had the virus.
"We decided to go and get tested because that was what the Government was pushing to do, so we did," Francesca said.
"But we were thinking 'surely this is not COVID', it was just like a game for her. She was very excited about it."
But the next day, Francesca and her husband also experienced flu-like symptoms, and they too went to be tested.
The following day, they heard from the department that Beatrice was positive, and they had no doubt that they had it too.
"I was scared because I knew that in kids COVID is not too nasty, but you never know," she said.
"Then because we were sick, I'm like, 'OK, we are more likely to get severely sick and if that happens, and if one or two of us have to go to the hospital who is going to look after ... a positive kid?'
Within days, the whole family had tested positive for the virus.
"Back then, I was still breastfeeding her. Camilla was the last one to test positive. I truly never contemplated putting myself in a room and her in another room," she said.
"Those few days before we knew she was positive, we didn't really try hard to maintain distance because I thought that would have been much, much worse than probably having COVID, considering how well she was, and we have a little house."
Over the next ten days, Francesca and Alessandro suffered severe fatigue, headaches and a sore throat, while their kids remained relatively well.
While friends left meals and gifts on the doorstep, Francesca rang a doctor friend who worked at the Royal Children's Hospital for reassurance, who put her onto the MCRI research team.
Francesca, a statistics researcher at MCRI herself, was passionate about being part of the quest to gather more information on the virus.
"It was a bit difficult for Camilla, but we managed to give weekly blood, urine, saliva and the swab samples. We had a nurse coming in for the blood ... everything else, I did myself on them and myself."
The family, like others involved in the study, will continue to be followed in the coming months to see if they still have immunity to the virus.
"We were immune, all the four of us, at three months, which was very reassuring," Ms Orsini said.
"We are still waiting for the six months blood test to see whether we are still immune or not. I hope we're still immune."
With trials of COVID-19 vaccines on children currently taking place overseas, Dr Neeland is also interested to see if the immune responses her team found are replicated when children are given the vaccine.
"In the context of infection, we are showing quite robust immune responses in children ... it'll be really interesting to see how that is mimicked in a vaccination setting."
Children and adults test negative in infected households
Last year, the researchers studied another Melbourne family, where the parents had both tested positive for the virus, but their young children had not.
That study found that despite never testing positive for coronavirus, the children had successfully mounted an immune response to it.
Dr Neeland said the most recent study backed up those earlier results.
"Our study supported those findings showing that other children who have been exposed and negative show a change in the immune response," she said.
"But really what this added was looking at a really extensive number of children who were positive."
Dr Neeland said while all members of the infected households they studied showed some sort of immune response to the virus, it was not clear why some got the virus and others didn't.
"We're still trying to work out why some children have the same exposure and can be protected and some children have exposure and can test positive," she said.
"But I think what's comforting is that the majority of the children that we've seen have really mild COVID-19 if they do test positive."
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