How kids’ immune systems can evade COVID

How kids’ immune systems can evade COVID Childrens’ untrained immune response seems to be key to eliminating SARS-CoV-2. Bianca Nogrady nature

Young children account for only a small percentage of COVID-19 infections¹ — a trend that has puzzled scientists. Now, a growing body of evidence suggests why: kids’ immune systems seem better equipped to eliminate SARS-CoV-2 than are adults’.

“Children are very much adapted to respond — and very well equipped to respond — to new viruses,” says Donna Farber, an immunologist at Columbia University in New York City. Even when they are infected with SARS-CoV-2, children are most likely to experience mild or asymptomatic illness².

Another clue that children’s response to the virus differs from that of adults is that some children develop COVID-19 symptoms and antibodies specific to SARS-CoV-2 but never test positive for the virus on a standard RT-PCR test. In one study, three children under ten from the same family developed SARS-CoV-2 antibodies³ — and two of them even experienced mild symptoms — but none tested positive on RT-PCR, despite being tested 11 times over 28 days while in close contact with their parents, who had tested positive.

Their immune system sees the virus “and it just mounts this really quick and effective immune response that shuts it down, before it has a chance to replicate to the point that it comes up positive on the swab diagnostic test”, says Melanie Neeland, an immunologist who studied the family, at the Murdoch Children’s Research Institute in Melbourne, Australia.

Even in children who experienced the severe but rare complication called multisystem inflammatory syndrome in response to SARS-CoV-2 infection, studies report that the rate of positive results on RT-PCR range from just 29% to 50%^4,5,6. ...