Immune System Clues to Why COVID Is Easier on Kids

FRIDAY, Sept. 25, 2020 (HealthDay News) -- Kids and adults have different immune system responses to infection with the new coronavirus, which may help explain why severe COVID-19 is more common in adults, researchers report.

For their new study, they examined blood and cell samples from patients admitted with COVID-19 symptoms to the Montefiore Medical Center in New York City.

The researchers found that the younger the patient, the higher their levels of two immune system molecules, interleukin 17A (IL-17A) and interferon gamma (INF-g).

IL-17A helps trigger immune system response during early infection and INF-g combats replication of the virus. Higher levels of the two molecules may be associated with better outcomes in COVID-19 patients, according to the authors.

"To our surprise, we found these particular serum cytokines were at higher levels in children than adults," co-senior study author Dr. Kevan Herold, a professor of immunology and internal medicine at Yale University, said in a Yale news release.

Researchers were also surprised to find that certain antibody responses thought to be protective were higher in adults, including those with severe COVID-19, than in children.

IL-17A and INF-g are part of the innate immune system, a more primitive, non-specific response activated early after infection. On the other hand, adults had a more vigorous adaptive immune system response, including higher levels of antibodies that attack the new coronavirus.

The findings suggest "that kids have a more robust, earlier innate immune response to the virus, which may protect them from progressing to severe pulmonary disease," said co-senior study author Dr. Betsy Herold, a professor of pediatrics and microbiology-immunology at Albert Einstein College of Medicine in New York City.

The study included children and teens with multi-system inflammatory syndrome (MIS-C), a rare complication of COVID-19 infection in young people that's associated with a range of severe health complications.

Like other youngsters, those with MIS-C also have high levels of IL-17A and INF-g, and rarely develop the severe lung damage seen in adults with severe COVID-19.

The findings suggest that boosting certain types of immune responses may benefit COVID-19 patients, the researchers said.

The study was published recently in the journal Science Translational Medicine.

More information

The U.S. Centers for Disease Control and Prevention has more on COVID-19.