From the early days of the coronavirus pandemic, scientists have observed that children appear to be less susceptible to developing COVID-19, although the exact reasons why this remains unclear.
Now an unusual case in Australia can give a unique idea of the mystery, thanks to the experience of a young family from Melbourne.
In this family of five, both parents became ill with COVID-19 after attending an interstate wedding without their children. However, the symptoms appear only days after returning from the trip.
Nevertheless, completely unknown to them, they had brought SARS-CoV-2 into their home and exposed their children to it.
Once both parents develop symptoms – including cough, nasal congestion, fever and headache – the whole family is tested for the virus. The parents’ tests returned positive. The children’s tests returned negative.
“It was incredibly amazing because they had spent a week and a half with us while we were COVID-positive,” mother Leyla Savenko told ABC News.
However, the really surprising part is yet to come.
Health workers asked the family to repeat the tests, but the children’s tests were again negative for SARS-CoV-2, although two of the boys in the family (aged 9 and 7) had mild symptoms.
The youngest child, a 5-year-old daughter, remained asymptomatic throughout the episode, although she often slept in the same bed with her parents during their illness (physical distancing measures are not possible in the household during their quarantine).
Intrigued by the children’s negative results while living so close to their infected parents, the researchers asked the family to take part in a study by analyzing blood, saliva, feces and urine samples and taking nasal and throat swabs every two to three days.
Surprisingly, despite repeated polymerase chain reaction (PCR) tests showing that children were consistently negative for SARS-CoV-2 PCR, the researchers found specific antibodies against SARS-CoV-2 in the saliva of all family members and in detailed serological tests.
In other words, the children never had a positive test for the virus, but some level of exposure to the virus still elicited an immune response inside them and one seemed to be able to fight off the infection.
“The youngest child who showed no symptoms at all had the strongest antibody response,” said immunologist Melanie Nyland of the Murdoch Children’s Research Institute (MCRI).
“Despite the active immune cell response in all children, the levels of cytokines, molecular messengers in the blood that can cause an inflammatory reaction, remained low. This was consistent with their mild or no symptoms.”
Fortunately, all sick family members recovered and did not need medical attention.
The mechanisms of children’s immune responses are not yet fully understood, but finding out how and why their immune responses were activated (in the absence of confirmed cases of the virus) may shed much light on children’s susceptibility to COVID-19 more generally .
“This study is something like our first step to take a really deep look at children’s immune systems and see which components may respond to the virus,” said study’s first author, pediatrician Shidan Tosif of the University of Melbourne. Age.
“The fact that these children were able to rule out the virus and did not even show a positive test result suggests that they have some level of immune system that is able to respond and deal effectively with the virus without ever having to. they get very sick. “
In fact, the researchers believe that the children were actually infected with the virus, but their immune system somehow managed to elicit an antiviral response that is very effective in limiting the replication of the virus, unlike their parents.
This immune response was so effective that it could have led to such a low load on the virus that it passed the sensitivity of the PCR test, which is another issue that needs further investigation, the team said.
“The discrepancy between virological PCR results and clinical serological tests, despite an apparent immune response, underscores the limitations of nasopharyngeal PCR sensitivity and current diagnostic serology in children,” the researchers wrote.
For Leila Savenko and her family, they are simply happy to have all the tampons and tests behind them and are excited to contribute in their own way to our better understanding of this pervasive virus and what it awakens in us.
“It was a ‘wow’ moment that despite the fact that the children were tested negative, they developed antibodies,” Savenko said. ABC News.
“You can just see the look on the doctors’ faces. They were completely amazed and really excited to think there was this discovery.”
The findings were reported in Nature Communications.