Differences in Novel Coronavirus Response Between Children’s and Adults’ Immune Systems

Novel coronavirus antibody levels in children infected with Novel Coronavirus SARS-COV-2 are low, but children also seem to clear the virus from their bodies faster than adults, according to a small Australian study.

Some children do not develop antibodies when they are infected with COVID-19

The new findings in Australia add to a growing body of evidence that children have a stronger initial immune response to Novel Coronavirus COVID-19 and can quickly clear the infection compared to adults, researchers said. But because antibodies may be important in preventing reinfection, the findings also raise concerns about how to protect children against future reinfection, given their low levels of antibodies.

The study, published March 9 in JAMANetwork Open, looked at 57 children with a median age of 4 and 51 adults with an average age of 37, These individuals tested positive for novel Coronavirus SARS-COV-2 between May 10 and October 28, 2020. Participants had mild symptoms such as headache and fever or were largely asymptomatic. The researchers measured participants’ viral RNA levels using nasal and pharyngeal swabs, and tested blood samples for antibodies to antiviral immunoglobulin G. They found that children and adults had similar viral loads, but only 37 percent of the children developed antibodies to novel Coronavirus SARS-COV-2, compared with 76 percent of adults.

Previous studies have also found different antibody responses in children and adults. An analysis by immunologist Donna Farber of Columbia University in New York City and her colleagues found that adults produce a broader range of antibodies than children, including more virus-blocking antibodies. The Australian analysis “confirms and extends these findings,” Farber said.

Violent reaction

Children may produce fewer antibodies because they have a stronger innate immune response than adults. It’s the first line of defense against pathogens, and it’s nonspecific immunity. Children are also better able to cope with infections that enter their bodies, such as through the throat or nose. This means the body can clear the virus quickly and it doesn’t “hang around” in the body, triggering an adaptive response that produces antibodies, Says Farber.

Other studies, including one by cytogeneticist Kristin Meyer of the Wellcome Sanger Institute in Hinxton, England, have shown that children develop stronger and faster responses to infections, and that the innate immune system plays a major role in this response. The younger the child, the more likely their innate immune system is to drive this response, Meyer said.

But Paul Licciardi, an immunologist at Murdoch Children’s Research Institute in Melbourne and co-author of the Australian study, says that when he and his team looked at innate immune cells in a small group of children, they did not find a stronger response in those who did not produce antibodies, which is worth studying.

The Australian team also measured levels of immune cells in the blood of some of the participants. They found that children had lower levels of certain types of antibody-producing memory B cells and memory T cells than adults. That suggests children have less specific immune responses, which are more targeted and produce immune memories, says Betsy Herold, a pediatric infectious disease doctor at Albert Einstein College of Medicine in New York City.

Uncertain protection

The team is concerned that if the children’s specific immune response is not as strong, it could put them at risk of reinfection. But Herold here urges caution: “We don’t have the data to draw that conclusion.” Children may not be protected from reinfection, but their risk of complications after the initial infection remains low, Meyer said.

The Australian study also only looked at people infected with an early variant of the Novel Coronavirus SARS-COV-2, but the results for the more infectious Delta and Omicron variants may differ. The child said, in the delta virus infection in 2021 for preliminary analysis, he and his team found that most children and adults will produce antibodies to fight infection, probably because the delta virus viral load higher, and Australia’s team is now collecting data of omega is cloned virus immunology, For further study.