Scientists examine kids' unique immune systems as more fall victim to Covid - CNN

Paul Offit, an expert on infectious diseases at Children's Hospital of Philadelphia, which — like other pediatric hospitals around the country — has been inundated with Covid patients.

Until the delta variant laid siege this summer, nearly all children seemed to be spared from the worst ravages of Covid, for reasons scientists didn't totally understand.

Although there's no evidence the delta variant causes more severe disease, the virus is so infectious that children are being hospitalized in large numbers — mostly in states with low vaccination rates.

"Answers can't come soon enough."

Investigating Immune Systems

For much of the pandemic, doctors could only guess why children's immune systems were so much more successful at rebuffing the coronavirus.

Despite the alarming number of hospitalized children in the recent surge, young people are much less likely to become critically ill.

Most children shrug off the virus with little more than a sniffle.

A growing body of evidence suggests that kids' innate immune systems usually nip the infection early on, preventing the virus from gaining a foothold and multiplying unchecked, said Dr.

(Both kids and adults usually make enough antibodies to thwart future coronavirus infections after natural infection or vaccination.)

While the adaptive immune system can be effective, it can sometimes cause more harm than good.

Like soldiers who kill their comrades with friendly fire, a hyperactive immune system can cause collateral damage, triggering an inflammatory cascade that tramples not just viruses, but also healthy cells throughout the body.

In some Covid patients, uncontrolled inflammation can lead to life-threatening blood clots and acute respiratory distress syndrome, which occurs when fluid builds up in the air sacs of the lung and makes it difficult to breathe, Betsy Herold said.

zzz that 4% to 11% of kids have persistent symptoms.

Unanswered Questions

Scientists have fewer clues about what goes wrong in certain children with Covid, said Kevan Herold, who teaches immunobiology at the Yale School of Medicine.

Research suggests that children have more robust innate immune systems than adults because they have experienced so many recent respiratory infections, within their first few years, which may prime their immune systems for subsequent attacks.

But not all children shrug off Covid so easily, Eils said.

"We had a 3-month-old who required ECMO," or extracorporeal membrane oxygenation, in which the patient is connected to a machine similar to the heart-lung bypass machine used in open-heart surgery.

Even previously healthy children sometimes die from respiratory infections, from Covid to influenza or respiratory syncytial virus.

But studies have found that 30% to 70% of children hospitalized with Covid had underlying conditions that increase their risk, such as Down syndrome, obesity, lung disease, diabetes or immune deficiencies.

An August study in Science Immunology reported that such "autoantibodies" contribute to 20% of Covid deaths.

Autoantibodies are very rare in children and young adults, however, and unlikely to explain why some youngsters succumb to the disease, said study co-author Dr.