From the very first days since the pandemic started, scientists have found that children seemed to be somewhat less likely to develop COVID-19, although the causes are still unclear.
Now, the special case of a young family in Melbourne (Australia) can help give us more insight into this matter.
In this family of five, the two parents became sick with COVID-19 after attending an interstate wedding without their children. However, the symptoms didn’t show until days after they had returned from the trip.
When the symptoms in the parents began to appear, including a cough, stuffy nose, fever and headache, the family decided to get tested. The couple positive for COVID-19, but their children were negative.
Leila Sawenko, the mother of the family told ABC News: “It was really miraculous because the children spent a week and a half with us, and by that time my husband and I had COVID-19.”
The health care staff asked the family for a second test, but the results from the children’s tests were still negative, even though two of the boys (a 9-year-old and a 7-year-old) did have mild symptoms.
The youngest child, a 5-year-old daughter, remained asymptomatic throughout the entire episode, even though she was frequently sleeping in the same bed as the parents during their sickness (physical distancing precautions not feasible in the household during their quarantine).
Scientists invited families to participate in a study, which analyzed samples of blood, saliva, feces and urine and took samples from the mouth with a cotton swab every 2-3 days.
Even though PCR tests were performed several times, the children remained negative for SARS-CoV-2. Researchers found the presence of SARS-CoV-2 antibodies in the saliva of all family members and in detailed serological tests.
In other words, the children in this family never gave a positive result, but exposure to the virus triggered an immune response and a response that appeared to be able to fight the infection.
“The youngest child, who showed no symptoms at all, had the strongest antibody response,” says immunologist Melanie Neeland from Murdoch Children’s Research Institute (MCRI).
“Despite the active immune cell response in all children, levels of cytokines, molecular messengers in the blood that can trigger an inflammatory reaction, remained low. This was consistent with their mild or no symptoms.”
According to the study’s first author, pediatrician Shidan Tosif from the University of Melbourne, told The Age: “This study is kind of our first step to look really in-depth at the immune system of children and to see what components may be responding to the virus”.
“The fact these children were able to shut down the virus and without even showing a positive test result suggests they have some level of their immune system which is able to respond and deal effectively with the virus, without them ever becoming very unwell.”
In effect, the researchers think that the children did become infected by the virus, but their immune systems were somehow able to mount an anti-virus response that was highly effective in restricting virus replication, unlike their parents.
That immune response was so effective, it could have brought the viral load so low, that it went under the sensitivity of the PCR testing, which is another issue that bears further examination, the team thinks.
“The discordance between the virological PCR results and clinical serological testing, despite an evident immune response, highlights limitations to the sensitivity of nasopharyngeal PCR and current diagnostic serology in children,” the researchers wrote.
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