Why Do Children Tend to Fight off COVID-19 Better Than Adults?
April 13, 2022
If there’s a silver lining to the pandemic, it’s that children have largely been spared the worst effects of COVID-19. Though children can become infected with SARS-CoV-2 (the virus that causes COVID-19) as easily as adults, most infected children experience mild symptoms or no symptoms at all. Why is this? Though the research is still evolving, recent studies have begun to shed light on why kids tend to fare better than adults against COVID-19.
First Line of Defense: Strong Innate Immunity
"Much of the recent research," says Amy Edwards, MD, a pediatric infectious disease specialist at UH Rainbow, “points to certain key differences between the immune systems of children and adults.”
The immune system, the job of which is to recognize and eliminate microscopic substances that invade our bodies, consists of two main parts: innate immunity and adaptive immunity. Innate immunity mounts the initial response against a germ, while adaptive immunity takes over when innate immunity is unable to eliminate the threat by itself. Though adaptive immunity is more targeted and accurate than innate immunity, it does not respond as quickly.
Some research has shown that a more vigorous innate immune response in children can eliminate SARS-CoV-2 infection largely without the help of the adaptive immune response. In a study published in Science Translational Medicine in 2020, researchers looked at blood samples from a group of adults and children infected with COVID-19 and found that not only did the children (who had milder symptoms than the adults) have lower levels of substances associated with the adaptive immune response in their blood, their blood also contained higher concentrations of substances associated with the innate immune response.
“These and similar findings,” says Dr. Edwards, “suggest that children’s innate immune response is often strong enough by itself to eliminate the SARS-CoV-2 infection without the need to call in reinforcements from the adaptive immune system.”
Another advantage related to innate immunity that children have is a much lower incidence of “cytokine storm” than adults. A cytokine storm is a life-threatening inflammatory overreaction in which the innate immune system attacks the lungs and/or other organs. Cytokine storms typically occur in adults during the second week of severe and life-threatening cases of COVID-19.
Benefits of a Less Developed Adaptive Immune System
Children also appear to have an advantage against COVID-19 as a result of their less developed adaptive immune systems. In particular, kids have more “naive” versions of T cells – soldier cells that hunt down and kill specific germs. By the time a person reaches their thirties, many of their naive T cells will have encountered specific pathogens and changed into “memory” T cells, which can respond rapidly when the same pathogen or a structurally similar pathogen enters the body.
As people age and more of their naive T cells change into memory T cells, the body decreases its production of naive T cells. Consequently, adults have fewer naive T cells to recognize and fight new pathogens like SARS-CoV-2.
Though evidence is inconclusive at this point, some studies have shown that children’s nasal passages contain less of the angiotensin-converting enzyme 2 (ACE2) receptor than adults. Acting as a cellular doorway and entry point for COVID-19, ACE2 is a protein to which SARS-CoV-2 binds in order to enter and infect the cells lining our airways.
Another factor contributing to the lower incidence of severe disease observed in children with COVID-19 is that children are less likely to have underlying chronic health conditions such as obesity and diabetes that increase vulnerability to the more severe effects of the disease.
Vaccination Is Still Important
Lower risk of acute disease in children with COVID-19 has discouraged some parents from getting their kids vaccinated.
“While kids do fare better overall against COVID-19 than adults,” say Dr. Edwards, “it is important to note that some children who acquire the disease experience uncomfortable long-term symptoms, serious complications, hospitalization and even death due to the infection.”
As such, public health experts continue to emphasize the importance of getting your children vaccinated to protect them while also helping save the lives of others by reducing the spread of infection.
Initial research suggests that fewer children than adults develop fever, cough, or shortness of breath or need hospitalization with COVID-19. However, severe illness has been reported in children with COVID-19 -- most often in infants younger than a year old. Learn more about the impact of coronavirus in children and young adults.