2023-10-14 02:00:00
Recently, American scientists discovered the reason why infants and young children pass COVID-19 more easily than adults. The photo shows a child visiting the Songpa-gu Public Health Center in Seoul collecting a sample for a COVID-19 PCR test./News 1
American scientists have discovered the reason why infants and children have milder symptoms than adults when they contract COVID-19. Until now, experts have speculated that this may be because children’s immune systems are less developed than adults, but it was found that the exact reason lies in ‘the speed at which antibodies are produced’ and ‘antibody diversity’.
Researchers at Stanford University School of Medicine in the U.S. announced on the 13th (local time) that they compared the immune responses of adults and infants under 2 years of age when they each contracted COVID-19, and found that adults had more diverse antibodies and had more severe infection symptoms. .
The more active the immune response is to COVID-19, the more severe symptoms such as runny nose, cough, and high fever become. Adults who get infected with COVID-19 even following receiving the COVID-19 vaccine experience tearing pain in the throat, stuffy nose, chills, headaches, etc., and in severe cases, they may even lose their sense of taste or smell. On the other hand, for infants and young children, it passes like a mild cold. In fact, in the United States, 6% of those infected with COVID-19 are infants and children under the age of 5, and more than 90% of them have suffered from COVID-19, but they account for less than 0.1% of COVID-19 deaths.
Researchers obtained nasal and blood samples from 54 infants who had COVID-19 before their second birthday and 27 infants who had never had COVID-19. They then compared it with data from dozens of adults who had previously had COVID-19.
As a result, it was found that when infected with COVID-19, antibody levels rapidly rise to the highest level in adults, but increase more slowly in infants and young children. The adult’s antibody level remained at the highest level for regarding six months and then decreased to one-tenth. In infants and young children, antibody levels increased more slowly, but reached a peak level similar to that in adults.
Additionally, the diversity of antibodies produced in the blood was much greater in adults. In fact, infants and young children had very low antibody diversity and had low immunity to anything other than the virus they had contracted. In other words, infants and children who have been infected with the COVID-19 delta mutation can be more easily infected with the Omicron mutation than adults.
“Elderly and children are the most vulnerable population groups to almost all infectious diseases, but unlike the elderly, children survive well,” said Valley Fullerdren, a professor in the Department of Microbiology, Immunology and Pathology at Stanford University School of Medicine. “Until now, we did not know much regarding the specific causes.” .
In addition, the researchers found three other reasons why children have much milder symptoms when infected with COVID-19. One is that in infants and young children, the number of receptors that the COVID-19 virus can attach to the surface of respiratory cells in the nose and bronchi is much smaller. Another cause is that the level of signaling proteins that promote inflammation in the blood is much lower in infants and children than in adults.
It was also pointed out that when the COVID-19 virus enters the nose, neutrophils, which are immune cells that are produced faster than antibodies and directly fight the virus, are more activated the younger you are. Because the virus is caught to some extent in the nasal cavity, the number of cases that pass through the bronchi and into the lungs is much lower.
The researchers expected that by paying attention to what happens in the nasal passages, bronchial tubes, and blood when infants and young children are exposed to the COVID-19 virus, they will be able to develop effective treatment methods for other mutations that may appear in the future. For example, a drug that can attack viruses similar to the immunity of infants and children is sprayed into the nasal cavity.
However, it is assessed that additional research is needed on other respiratory viruses. Respiratory syncytial virus (RSV) and influenza are different from COVID-19 in that infants and children suffer from much more severe symptoms than adults.
The results of this study were published in the 13th issue of the international academic journal Cell.
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