A curious feature of the new coronavirus is that it rarely causes severe symptoms in children. Some other respiratory viruses, such as influenza and respiratory syncytial virus (RSV), are especially dangerous for both the very old and the very young. But this new virus, which can be lethal in the elderly, spares the vast majority of young children.
At first it seemed that few children were getting infected with the new virus, but that view has changed as more is learned about the pathogen.
“As we get more information and have more experience, there are a lot of reports of children who are carrying the virus who are asymptomatic,” says Sallie Permar, MD, PhD, professor of pediatrics, molecular genetics & microbiology, immunology, and pathology and member of the Duke Human Vaccine Institute.
“It may be that children are susceptible to getting the infection, but they respond in a way that doesn’t render them severely ill,” Permar says. She is aiming to discover just how the immune system in children responds to the new virus, which could inform treatments and vaccines for people of all ages.
Permar has studied the immune system for years with the goal of preventing viral infections in newborns. “What I’ve come to appreciate is how different the immune landscape of the infant and young child is from that of adults,” she says.
Before birth, the immune system of the fetus is muted to avoid rejecting the mother, who shares only 50 percent of the fetus’s genes. But as soon as the baby is born, its immune system must quickly ramp up to attack pathogens.
Permar says certain aspects of a young immune system lag behind an adult’s, but other parts are ready right from the start. “Perhaps that exact mixture of immune readiness is what leads to a child being able to contain the coronavirus and not develop the severe pneumonia,” she says. “And understanding children’s responses could be an important guide for the coronavirus vaccine.”
Permar has begun an important first step to understanding the new virus through a laboratory study focused on the course of the disease in young and adult non-human primates. “That will help us understand how it is that young individuals in our population are fairing better,” she says.
“We also want to look at how this disease is playing out in the human population,” she says. Working through the Children’s Health and Discovery Initiative, which Permar directs, Duke researchers have begun a study to follow children with a parent or sibling who has tested positive for COVID-19. The study is led by Jillian Hurst, PhD, adjunct assistant professor of pediatrics, and Matthew Kelly, MD, MPH, assistant professor of pediatrics.
Permar says the observational study will follow the children to see whether they become infected, and, if they do, whether they develop symptoms, how their immune systems respond, and how long the virus is detectable in their nose and in their stool.
“We think it’s important to understand how a child responds to this infection, because finding ways to make adults and the elderly more childlike in response to this infection could get us out of the hot water we’re in,” Permar says.