Children’s innate immune system helps fight off the virus more effectively than that of adults • But is this a reason not to vaccinate children?
The apparent immunity of children to the most severe effects of the corona was one of the mysterious – and alleviating – things of the plague. Now the reasons for this are becoming clear, scientists say. Children activate the first line of defense, known as the innate immune system, more effectively than adults.
Although there have been children who became seriously ill after being infected with corona, most children have mild symptoms or no symptoms at all. Unlike other respiratory viruses such as influenza or hRSV, the corona virus in children is not even close to its severity in adults or the elderly.
The lower risk to children caused some parents to hesitate to vaccinate their children. Immunization rates among children eligible to receive them lag far behind the level of immunization in adults.
Public health experts say they want to explain the scientific reasons why vaccines give children better protection against corona, and still emphasize the importance of vaccines in protecting vulnerable children and containing infections. The amount of corona hospitalizations in children peaked in January, when the Omicron strain infected many more people than at previous plague peaks.
“Some people get it pretty hard,” Lee Bears, a member of the American Academy of Pediatrics and a professor of pediatrics at Washington National Hospital for Pediatrics, told me.
The immune system is made up of different lines of defense: the innate immune system coordinates the initial response against infection, while the adaptive immune system develops more slowly and creates more specific defenses.
Like cannonballs fired at the beginning of the invasion
To understand why children cope with the corona better than adults, imagine the immune system as a medieval fortress, said Kwan Harold, a professor of immunobiology and internal medicine at Yale University. The innate system, which includes the lining of the nose and throat that helps capture harmful microbes, is like the canal around the fort, preventing intruders from entering. The innate immune system also includes proteins and cells that activate the primary immune system. Harold compares them to cannonballs fired at the opponent at the beginning of the invasion.
A second line of defense, the adaptive immune system, includes T cells and B. The adaptive system takes longer to build a response, but it can remember specific weaknesses of past invaders. Think of this system as soldiers preparing for battle inside the fort, Harold said.
The innate immune system has no such memory. It relies on patterns associated with more harmful microbes in general. Immunologists have found that children’s immune systems have higher levels of some innate molecules, and as a result their immune response is stronger compared to that in adults. Experts like Dr. Harold and his wife, Betsy Harold, a pediatric infectious disease doctor at the Montefiore Children’s Hospital in the Bronx, think this is why children’s children can better fight the virus that causes coronary heart disease.
When Corona hit all of New York City in early 2020, the Harolds began trying to figure out why so many adults come to Corona hospitals compared to children. Along with other researchers, they began studies examining children’s immune systems, first approaching what Betsy Harold called the lowest fruits: cytokines – small proteins produced by a variety of cells that help them communicate with each other.
Two important cytokines for the innate immune system are less present in the blood of older people compared to younger ones, they found. “This is where the idea began to develop that it was a response of the innate immune system,” Betsy Harold said.
The Harold study compared 65 young and 60 adults with corona in New York City, and found that children rely less on the adaptive immune system than adults, probably because they have a stronger congenital response.
They also examined 12-child and 27-adult markers, and found that more genes involved in the innate immune system were activated in the children, who also had higher levels of cytokines associated with the innate immune system.
Lack of immune memory
It is also possible that compared to adults, children have an advantage precisely because of the lack of immune memory when it comes to the war in Corona, said Amy Chong, a researcher at the Peter Doherty Institute for Infections and Immunity in Melbourne, Australia. After exposing the blood of healthy people to the corona virus, she and her colleagues found that healthy older people had a strong antibody response to the corona, apparently because they had been exposed many times before to other corona viruses, such as those that cause simple colds.
Children, on the other hand, do not have a strong existing antibody response, Dr. Chung said, because they have been exposed to at least some types of corona viruses in the past. While this may not seem like a good thing, in this case it has an advantage: CoV-2, their immune system fought the vital components of the virus immediately.
The immune system of older people is more vulnerable to parts of the virus that may have encountered other viruses from the same family. “These parts probably aren’t that important in stopping the infection,” Chung said.
Vaccinate or not vaccinate
The relative immunity of children to Corona has caused some parents to prevent their children who can get the vaccine from receiving it. The Kaiser Family Foundation recently conducted a survey of 420 parents, and found that half of them are not so worried or are not at all worried about the possibility that their children will start in Corona severely.
Kate Simmonds said she has no plans to vaccinate her children, aged two years and nine months, when they will be eligible to receive the vaccine, because of the relatively low risk of serious illness, and because she is concerned about possible adverse effects of the injections.
“If it was a disease that affects young people more than adults, maybe my opinion would have been different, but that’s not the case,” said Simmonds, a 40-year-old living in Kenandaiga, New York. She said her husband was vaccinated, and she was not vaccinated.
Immunization rates in people under the age of 18 are slightly lower than in adults, according to the Disease Prevention and Disease Study (CDC). About 40% of children eligible to receive the vaccine are fully vaccinated, compared to about three-quarters of adults who can receive it.
The researchers found no evidence that corona vaccines pose any serious safety concerns. In experiments performed on thousands of children, the most common side effects of the vaccine were mild, and had no lasting effects, the CDC said.
Corona vaccines are not yet available for children under the age of 5. U.S. health regulators have delayed testing of Pfizer and Biontech’s coronary vaccine for this age group because at the time of the trials the two-dose series did not appear to be as effective against strain. Omicron.
Even if vaccines are available to this young age group, only 31% of parents of children at that age say they would vaccinate their children immediately, Kaiser’s survey found. About a quarter of parents say they would not have stored their children anyway.
But children are more likely to be infected with corona than adults, according to recent studies, and children appear to be more effective as spreaders of the virus than previously thought.
Some children are hospitalized because of corona and others who continue to have symptoms long after they have died from the virus, Betsy Harold said. Children are also at risk for multisystem inflammatory syndrome, or MIS-C, a rare condition that can occur in children a few weeks after being infected with corona. MIS-C can cause tissue damage or even death.
“Homeland Security does not protect 100%,” Betsy Harold said.
While this is a good protection, she said, the corona is still dangerous to children, including the possibility of persistent symptoms. Without a vaccine, she said, “there’s a gamble on that.”