Why don’t kids get Covid badly? Scientists are starting to understand

LONDON — One of the enduring mysteries of the Covid-19 pandemic, a global health crisis that has led to over 6 million fatalities, is that children have been spared by the virus — for the most part — and have not experienced anywhere near the severity of illness that adults have.

When Covid emerged in late 2019 and began to spread around the world, scientists scrambled to understand the virus and how to combat it, with hospitals trying different techniques to save the worst-off Covid patients in intensive care units.

Mercifully, few of those patients were children, posing a mystery for public health experts as to why kids were not becoming severely ill or dying with Covid.

Scientists are still somewhat baffled as to why children are not badly affected by Covid, although studies are slowly shedding light on how, and why, children’s responses to Covid differ from those among adults.

“A number of theories have been suggested, including a more effective innate immune response, less risk of immune over-reaction as occurs in severe Covid, fewer underlying co-morbidities and possibly fewer ACE-2 receptors in the upper respiratory epithelium — the receptor to which SARS-CoV-2 [Covid] binds,” Dr. Andrew Freedman, an academic in infectious diseases at the U.K.’s Cardiff University Medical School, told CNBC in emailed comments, adding that nonetheless the phenomenon was not “fully understood.”

He noted more research will be required before we have a definitive answer but a body of evidence has already emerged showing that Covid poses a much smaller risk to kids, and why that might be.

In particular, the risk increases for people in their 50s and increases again for those in their 60s, 70s, and 80s, the Centers for Disease Control and Prevention says, with people 85 and older the most likely to get very sick. Having certain underlying medical conditions can also make adults more likely to get severely ill.

There have been several recent studies looking at the difference between adults’ immune response to Covid, and children’s, and these have found fundamental differences between the two with the latter having a more robust and “innate” immune response.

Research carried out by the Wellcome Sanger Institute and University College London, and published in the Nature journal in December, found a stronger “innate” immune response in the airways of children, characterized by the rapid deployment of interferons — which are released in the presence of viral or bacterial threats and help to restrict viral replication early on — UCL said.

Meanwhile in adults, the researchers saw a less rapid immune response which meant the virus “was better able to invade other parts of the body where the infection was harder to control.”

Kristin Mondy, a division chief of…